Seam Height, COR, and Compression Explained for Coaches
COR (coefficient of restitution) measures how lively a ball is off the bat, compression measures how much the ball resists deforming under force, and seam height affects grip and pitch movement — together, these three specs are what actually separate one baseball or softball from another once material and league approval are accounted for.
What each spec means
| Spec | What it measures | Why it matters |
|---|---|---|
| COR (coefficient of restitution) | How much energy the ball returns on contact — higher COR means a livelier, faster-coming-off-the-bat ball | Governing bodies set COR limits by level of play to keep competition consistent and safe |
| Compression | How much force it takes to deform the ball — higher compression means a harder ball | Affects feel off the bat and is often matched to player age and strength level |
| Seam height | How raised the stitching sits above the cover | Raised seams give pitchers more grip for breaking pitches; low seams are common for some higher-level and machine-feed balls |
Why this matters when choosing a ball
Governing bodies — NFHS, USSSA, USA Softball, and youth leagues among them — set specific COR and compression requirements for their approved balls, and these limits vary by age group and level of play. A ball’s seam height is more a matter of preference and intended use — raised seams for pitcher grip, low seams often preferred at higher levels of play. None of these specs can be judged from a product photo; they should be confirmed against the specific model’s published specifications.
A simple way to decide
- Start from the governing body and age group the ball needs to be approved for — this sets the COR and compression range.
- Choose seam height based on whether pitcher grip (raised seam) or a lower-profile ball (low seam) matters more for the intended use.
- Confirm the exact COR, compression, and seam specification against the current catalog listing for that model.
This guide reflects ProNine Sports’ current product specifications as of September 2026. Always confirm COR, compression, and seam specifications against the current catalog and the governing body’s current requirements before purchase.
