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Roto Grip Perfect Gem specs
The Roto Grip Perfect Gem is a solid reactive ball with the Gem AI core. Here are its published specs, how they compare with the other current balls in our table, and what the numbers mean on the lane.
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| Coverstock | ER1 Solid |
|---|---|
| Cover type | Solid reactive |
| Core (weight block) | Gem AI |
| Core type | Asymmetric |
| RG | 2.490 |
| Differential | 0.055 |
| Mass bias / intermediate diff. | 0.017 |
| Factory finish | 2000 Grit |
| Flare potential (maker) | High |
| Maker's category | HP4 |
| Color | Pink/Rose/Onyx |
| Release date (maker) | 10/02/26 |
| USBC approved | 8 September 2026 |
Numbers as Roto Grip publishes them, checked 21 October 2026. Roto Grip doesn't say which ball weight these numbers are for. Drilling changes how a ball behaves, so a pro shop's layout matters as much as these numbers.
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What the numbers mean
RG 2.490. That is lower than 57% of the 134 current reactive and urethane balls in our table, so it sits on the low side. Storm says "a low RG ball will rev up quickly and roll smoothly."
Differential 0.055. Higher than 85% of the balls in our table. Storm says "a high differential ball will create a sharper angle of entry into the pins."
Solid reactive cover. Storm says solid covers are "particularly effective on fresh oil patterns," and bowling.com calls them best on heavier oil.
Asymmetric core. Storm says asymmetric balls have "varying RG values along different axes" and more angular motion.
USBC allows an RG from 2.447 to 2.813 inches and a differential of at most 0.060 inches (Equipment Specifications Manual, March 2026). Our ball spec table lists every current ball we track, and who makes bowling balls covers which company owns Roto Grip.
Balls with similar numbers
Same cover type, closest RG and differential in our table:
- Track Paragon Fire: RG 2.486, differential 0.056
- Motiv Raptor Reign: RG 2.480, differential 0.055
- Roto Grip Wicked Gremlin: RG 2.500, differential 0.056
- Motiv Forge Fuel: RG 2.470, differential 0.055
Sources: Roto Grip product page; Storm, "Inside The Bowling Ball"; Storm, "The Coverstock"; bowling.com coverstock FAQ; USBC Approved Ball List (20 October 2026); USBC Equipment Specifications Manual.