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Hammer Black Pearl Urethane specs
The Hammer Black Pearl Urethane is a urethane ball with the LED 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 | Urethane Pearl 78D |
|---|---|
| Cover type | Urethane |
| Core (weight block) | LED |
| Core type | Not stated |
| RG | 2.650 |
| Differential | 0.015 |
| Factory finish | 500 Siaair Micro Pad |
| Maker's category | Mid Performance |
| Color | Black Pearl |
| Weights | 16-12 Pounds |
| Release date (maker) | March 21, 2024 |
Numbers as Hammer publishes them, checked 21 October 2026. Published for a 15-pound ball. 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 2.650. That is lower than 1% of the 134 current reactive and urethane balls in our table, so it sits on the high side. Storm says "a high RG ball delays its revving, offering more length and angular motion down the lane."
Differential 0.015. Higher than 2% of the balls in our table. Storm says "a low differential ball tends to have a more predictable, controlled motion."
Urethane cover. Storm says urethane covers "displace oil rather than absorbing it" and are a popular choice for spares and shorter oil patterns.
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 Hammer.
Balls with similar numbers
Same cover type, closest RG and differential in our table:
- Hammer Purple Pearl Urethane: RG 2.650, differential 0.015
- Storm Mix: RG 2.680, differential 0.006
- Storm !Q Tour 78/U: RG 2.650, differential 0.035
- Hammer Purple Pearl Urethane 78D: RG 2.632, differential 0.034
Sources: Hammer product page; Storm, "Inside The Bowling Ball"; Storm, "The Coverstock"; USBC Equipment Specifications Manual.