You Bought the Balls. Here's How to Use Them.
A no-nonsense guide to the GPS Soft-Shell Weighted Ball Set from the coaches who designed it. Built for pitchers, parents, and coaches who want a smart, safe way to start.
Designed and used daily at Grady's Pitching School inside Velocity Sports, Canal Fulton and North Canton, Ohio
Want the One-Page Version? Print It.
We put the weight chart, the progression rule, and a sample warm-up on a single sheet you can clip to a fridge, a clipboard, or a bullpen wall. Take it to the field, follow it for a week, and come back when you want more.
Start Here
If you just unboxed the set, this is your first 10 minutes. Do not skip it.
Your set ships with 6 balls (32 oz, 21 oz, 14 oz, 7 oz, 5 oz, 3.5 oz), a carrying case, and an inflation needle. If a ball ever feels soft, screw the needle into a standard football or volleyball pump and top off the ball through the small valve. Inflated firm, not rock hard.
You need a smooth, hard, flat surface roughly 8 to 12 feet away. The best plyo-wall material is horsemat. Any smooth wall will also work. Do NOT throw into a brick or cinderblock wall, the rough surface will tear the soft shell. Also avoid drywall, sheet metal, glass, and garage doors.
Aim at a spot on the wall at roughly head height and slightly to your throwing-arm side. Do NOT throw straight out in front of you. Throwing head high keeps the ball on a flat plane that mirrors your real release. Throwing arm-side keeps the rebound away from your face and glove side, which matters when you start working faster. Mark a target with tape if it helps.
The chart below tells you which weight to use for which job. The short version: heavier balls are recovery and constraint tools, lighter balls are arm-speed tools. Never start with the lightest ball.
Always work in descending order: heavy first, light last. This is non-negotiable.
You do not need more. Quality of intent beats volume every time.
Ball-By-Ball Weight Guide
Use this as your quick reference. Each weight has a job. Use the right tool for the job and stop trying to throw the heavy balls as hard as you can.
| Ball | Primary Use | Notes |
|---|---|---|
| 32 oz | Reverse throws and recovery | The heaviest ball in the set. Not a velocity tool. Use it for two-arm recovery throws into the wall after a bullpen or game. Builds posterior shoulder strength. Never throw it overhand for velocity. |
| 21 oz | Constraint throws, deceleration work | Pick this for slow, controlled constraint drills that retrain a long arm action. Throws should feel deliberate, not max effort. |
| 14 oz | Constraint and movement-prep | The "feel" ball. Excellent for movement prep before a bullpen and for short pivot or step-behind drills that isolate arm path. |
| 7 oz | Bridge weight for intent throws | Closest to a heavy-end intent ball. This is where most pitchers start the "intent" portion of a session. Throw with full effort, but keep mechanics clean. |
| 5 oz | Standard intent throws | Game weight (a regulation baseball is 5 oz). Use this to anchor your velocity work in the real ball weight you actually pitch with. |
| 3.5 oz | Underload, arm-speed throws | The light ball. Trains arm-speed cueing. Always last in the progression. A few high-quality throws, never a marathon. |
Pro tip: You do not need to throw every weight every day. A typical session uses three to four weights, not all six.
The Two Rules That Matter Most
Whether you are doing recovery, constraint work, or intent throws, you start with the heaviest ball you plan to use and finish with the lightest.
Why: Heavy balls down-regulate the nervous system and load the arm. Light balls up-regulate and create arm speed. Reversing the order trains your arm to slow down at the moment you need acceleration.
The set is not designed to be a long-toss replacement. It is designed for short, repeatable, high-quality reps that teach the arm a specific job.
3 throws for constraint or recovery, 4 to 5 for intent work. Stop if any throw breaks down mechanically. Reset, lighter ball, try again.
Track your volume. More is not always better. You have to manage your workload. Useful caps:
- Typical pre-throw routine: 25 to 30 weighted-ball throws.
- Full plyo warm-up: 50 to 60 throws.
- Mound day plyo cap: 30 to 40 throws.
- Medium-intent day cap (plyos plus catch play combined): under 75 throws.
5 throws at each weight across all 6 weights is 30 throws by itself. Volume adds up faster than it feels. Write it down.
Three Honest Use Cases
We do not sell this set as a prescriptive velocity program. We sell it as a tool. Here are the three jobs it actually does well in our facility every week.
Warm-Up & Movement Prep
Two to three minutes of arm circles and band work, then 3 throws each at 14 oz, 7 oz, and 5 oz into the wall from a standing pivot. Light effort. The body warms up faster than a long catch and the arm is primed for a bullpen.
Recovery After Bullpens or Games
After throwing, run the recovery sequence with the 32 oz gray ball:
- Reverse throws into the wall, both right side and left side
- Ball drops, 30 reps out in front and 30 reps to the side
- External rotation flip ups, 15 per set
All low intent. Decel and proprioception work, not strength work. Helps the back of the shoulder and the small stabilizers around the rotator cuff. Add 10 to 15 light rebounders at the end if you have a small trampoline.
Constraint & Cue Training
When a pitcher has a specific arm-path issue (short arm, pushing, flying open), the 21 oz and 14 oz balls give the body proprioceptive feedback for feel work. The goal is to improve arm action and feel a smoother, more on-time throw. All throws are done at very low intent. Used with a coach or a video setup, not as a guess.
Safety First. Read This.
We get asked the same questions over and over. Here are the honest answers.
Use only the 3.5, 5, and 7 oz balls for throwing. The heavier balls (14, 21, and 32 oz) are for arm care work only, things like reverse throws, ball drops, and external rotation flip ups. Do not throw the heavier balls overhand at this age.
Most sessions use all of the weights when running the recommended drill lineup. The set is built so each ball does a specific job (recovery, constraint, bridge weight, intent), and a complete HS warm-up touches each one.
Then it is too heavy. Drop down a weight. A ball that forces you to push or short-arm is training the wrong pattern.
Yes, into a heavy backstop net. Avoid thin batting cage netting and never throw into a screen with a person standing close behind it.
Most pitchers in-season: one or two short sessions a week, mostly warm-up and recovery. Off-season: two to three sessions a week as part of a full program.
Seamed balls give a more realistic feel of a baseball, which helps when you want grip and tactile feedback through the throw. Note: plyo balls are not recommended for working on spin or off-speed pitches. Save spin and breaking-ball work for actual baseballs.
Yes. The heavy balls are useful for soft-toss and short flips that train barrel control. Same rules apply: heaviest first, then down, and do not over-do it.
The GPS Plyo Drill Library
These are the plyo drills GPS pitchers run every week. Click any drill to expand.
Three rules on intent: Heavy plyos (14, 21, 32 oz) stay at 50 to 60 percent effort. Most warm-up days top out at 80 percent with the light balls. Build to 100 only on true high-intent days. If your arm feels off during warm-up, lower the intent or skip.
Ball color reference: Gray = 32 oz / Green = 14 oz / Yellow = 7 oz / Orange = 5 oz (game weight) / Red = 3.5 oz. (The 21 oz ball is not color-coded.)
1. Reverse Throws
What it teaches: Reverse throws help you feel how to load the scap and accelerate the arm in a clean pattern without relying on forward momentum. By removing rotation and stride, the drill isolates the upper body and teaches you to initiate the throw with a strong scap load, trunk extension, and smooth acceleration path. Key drill for arm path awareness and the foundation of an efficient arm action.
Setup & Action: Stand 6 feet from the wall, facing away. Hold the ball with both hands. Swing it overhead and back, releasing behind you into the wall like a reverse soccer throw-in. Catch the rebound, reset.
Cue: "Two-hand glove-side rip." Common mistake: going one-handed or going too hard. This is recovery and decelerator work, not strength work.
2. 10-Toes Drill
What it teaches: The 10-toes drill simplifies the throwing motion by removing all lower-half movement, requiring you to throw while standing tall and facing the target. This constraint demands efficient trunk rotation and arm action without momentum or stride. Useful for upper body rhythm, reinforcing direction, and building trunk strength and stability through a throw.
Setup & Action: Square both feet to the wall on the same line, 8 to 10 feet away, ball at the throwing-side ear. With no stride, rotate the trunk and throw into the wall. Catch the rebound, reset, repeat.
Cue: "Trunk leads, arm follows." Common mistake: drifting the feet to cheat the rotation. Keep them planted.
3. Marshall Drill
What it teaches: Marshall drills begin by staggering the feet, the drive leg set first, followed by the plant leg, creating a position with the hips open and shoulders closed. This setup encourages strong hip-to-shoulder separation and reinforces trunk rotation over trunk tilt. The drill limits stride and timing variables, helping you feel efficient energy transfer from the lower half while maintaining a clean, compact arm path. Especially useful for sequencing, direction, and avoiding excessive layback or early torso rotation.
Setup & Action: 6 to 8 feet from the wall, drive-leg foot set first behind the plant-leg foot. Hips open. Shoulders closed. Ball at a high cocked position. Throw into the wall with the ball-side hip already rotated.
Cue: "Pick the wall." Common mistake: trying to throw hard. The point is the position, not the velocity.
4. Pivot Pickoffs
What it teaches: Pivot pickoffs teach proper hip-to-shoulder separation, direction, and lead leg block. The drill removes stride and simplifies rotation so you can focus on staying closed with the torso while firing the lower half aggressively. Especially useful if you spin off early or struggle to drive energy down the mound efficiently. The finish should feel firm and balanced, with full trunk rotation and a strong glove side.
Setup & Action: Glove side to the wall, athletic stance, 8 to 10 feet away. Pivot the back foot like a pickoff move, throw into the wall in one motion. Reset, repeat.
Cue: "Pivot and pick." Common mistake: slow pivot. The pivot is the drill, make it sharp.
5. Roll-In Drill
What it teaches: Roll-in drills use momentum from a short step to teach tempo, timing, and full-body sequencing. They challenge you to build energy through the lower half, stay stacked through the throw, and block efficiently with the lead leg. The drill also exposes any disconnect between stride and rotation, making it useful for timing and intent without max effort.
Setup & Action: 10 to 12 feet from the wall, glove side to the wall. From a slight roll-in step, plant the front side and throw into the wall in a smooth, connected motion.
Cue: "Smooth in, smooth through." Common mistake: rushing the front side. Pushing the back leg too hard makes the drill feel pushy because the hips are already rotated forward.
6. Rocker Variation
What it teaches: Rocker drills blend momentum and sequencing by starting from a grounded, semi-dynamic position that mimics the stride phase of a delivery. You rock back and forth to build rhythm, then throw while focusing on trunk rotation and energy transfer into a firm front side. Rockers connect lower-half drive to upper-half rotation while staying directional and balanced through release. This is the bridge between warm-up plyos and intent throws.
Setup & Action: 10 to 12 feet from the wall in a rocker position. Rock back, transfer forward, throw into the wall at a target. Typical split: 5 at 7 oz, 5 at 5 oz, 5 at 3.5 oz.
Cue: "Full throw, easy face." Common mistake: skipping to 3.5 oz first. Always work heaviest to lightest.
7. Walking Windup
What it teaches: Walking windups are a dynamic progression that mimics a full delivery while exaggerating rhythm and fluidity. You walk into a controlled windup, focusing on smooth transitions between load, stride, and rotation. A blend of mechanical flow and intent training that improves tempo, feel, and athleticism. Especially useful if you tend to get rigid or robotic in your delivery.
Setup & Action: 12 to 15 feet from the wall, fully warmed up. Small walking step, transition into a normal windup, throw into the wall at game-like effort.
Cue: "Smooth feet, fast finish." Common mistake: tight face or clenched body. If your face is tight, your arm is tight.
8. Step Behind Throw
What it teaches: Loads the back hip and the glute (not the quad). Outputs raw arm speed inside a controlled lane. Closest thing to a max-effort intent throw in the wall plyo menu.
Setup & Action: Athletic ready position, 10 to 12 feet from the wall. Short step-behind shuffle, plant the front side, throw into the wall.
Cue: "Load the back hip." Common mistake: long step-behind that drains energy, or feeling the quad load instead of the glute. Keep the step short, sit into the hip.
Arm Care Drills
The drills below are not pitching drills. They are recovery and proprioception work designed to strengthen the small stabilizers around the shoulder and train decel. All use the 32 oz gray ball. Keep intent very low. These are the bones of every recovery-only session.
9. Ball Drops
What it teaches: Proprioception and grip / forearm endurance. Trains the arm to absorb and stabilize a heavy ball in multiple positions, which carries over to controlled deceleration in the throwing motion.
Setup & Action: Stand upright. For "out in front" reps, extend the throwing arm straight in front at shoulder height. For "to the side" reps, extend the arm out to the side. Hold the ball, let it drop, catch it as it falls. No wind-up. Quiet, controlled, smooth.
Cue: "Soft hands." Common mistake: tensing up or trying to snap the catch. Stay relaxed.
10. External Rotation Flip Ups
What it teaches: Rotator cuff endurance and external rotation control. Strengthens the deceleration chain and the small stabilizers that protect the shoulder during high-velocity throws.
Setup & Action: Standing or kneeling. Elbow tucked to the side at 90 degrees. Ball in the throwing hand. With the elbow stationary, externally rotate the forearm and flip the ball off the back of your hand at the top of the motion. Catch on the way down.
Cue: "Elbow stays, forearm flips." Common mistake: letting the elbow drift away from the body or swinging the whole arm. Keep the elbow locked in.
11. Rebounders (Requires a small trampoline)
What it teaches: Reactive strength and decel in a low-impact format. The trampoline absorbs the throw and rebounds the ball back, letting you stack reps without a partner or a hard wall.
Setup & Action: Requires a small angled rebounder or mini trampoline, 6 to 8 feet away. Two-handed reverse throw or one-handed light throw into the rebounder. Catch the rebound, reset. Skip this drill if you do not have a rebounder.
Cue: "Light into the bounce." Common mistake: throwing hard. This is decel work, not output work.
Sample Sessions
Starter Session (~25 throws)
Daily warm-up before a bullpen, lesson, or game.
- Reverse Throws / 32 oz / 5 reps / 50%
- Marshall Drill / 14 oz / 5 reps / 60%
- Rocker Variation / 7, 5, 3.5 oz / 9 total (3 each) / 70-80%
- Walking Windup / 5 oz / 6 reps / 80%
Full Pre-Throw Plyo Routine (~50 throws)
Complete pre-throw routine on a day when the ball set is your only throwing tool.
- Reverse Throws / 32 oz / 12 reps / 50%
- 10-Toes / 21 or 14 oz / 5 reps / 50-60%
- Marshall Drill / 21 or 14 oz / 5 reps / 60%
- Roll-In Drill / 5 oz / 10 reps / 50-60%
- Rocker Variation / 7, 5, 3.5 oz / 12 total / 80%
- Walking Windup / 5 oz / 8 reps / 80%
Recovery-Only Session
Day after a game or bullpen. Decel, proprioception, and posterior shoulder work, no intent throws. All work uses the 32 oz gray ball.
- Reverse Throws, right side / 8 to 10 reps / low intent
- Reverse Throws, left side / 8 to 10 reps / low intent
- Ball Drops, out in front / 30 reps / low intent
- Ball Drops, out to the side / 30 reps / low intent