Bowler Ratings


Bowler ratings are from 1 to 10 in order of Stroker (ST), Tweener (TW), Cranker (CR)

Note: Ratings are only available to our premium members.

General Info

Reviewed:March 2022
Coverstock Specs
Name:MicroTrax Solid Reactive
Type:Reactive Solid
Box Finish:2000 Abralon
Color:Citrine / Ruby / Amethyst
Core Specs
Name:Defiant LRG
Int. Diff:0.016

For details on our standard test layouts, please click here.

The Roto Grip Gem features the new Defiant LRG core and the very aggressive MicroTrax Solid Reactive coverstock. This strong reactive cover was seen previously in various formulations on balls like the Idol, Halo, and RST X-1. The Defiant LRG asymmetrical core is a modified version of the core that was found in the Defiant series of bowling balls. With Roto Grip’s lowest RG (2.47″) in an asymmetrical design, this is a core that is designed to rev up, and it is wrapped in coverstock that grips the lane with its rough 2000 Abralon box finish. All of these elements come together to create a ball that is made to hook.

Stroker loved the reaction he had with the Gem on our heavy oil test pattern. It easily allowed him to play more swing on the fresh than he usually can, thanks to the strong continuation at the back end. The dull finish and aggressive cover made sure the ball always hooked as he moved farther left in transition. There have been very few bowling balls that have given Stroker this kind of look on BTM’s slickest test pattern. Stroker had the best reaction of the three testers on our fresh medium pattern. The dull box finish

Additional Roto Grip Gem Resources

Click here to visit Roto Grip's website to read the manufacturer-supplied information on this ball. Also, see below for the manufacturer-produced promotional video for this ball.

Please remember that our reviews are solely based on our own testing and that you may sometimes find differences between our comments and ratings and the manufacturer's claims. Links to these manufacturer resources are provided here strictly for convenience purposes.

The BTM Ball Testing Team

About The BTM Ball Testing Team

The BTM Ball Testing Team is led by Eric Martinez. Our team of three testers has thrown and reviewed hundreds of bowling balls for Bowling This Month. When not testing balls for BTM, Eric owns and operates University Pro Shop in San Antonio, TX and he is an avid competitive bowler. Click here to learn more about how we test and review bowling balls.