- Purple Gem

First Impressions
The Roto Grip Purple Gem is a special release (often listed as an International Release) that technically picks up right where the massive success of the original Roto Grip Gem left off. Visually, as the name gives away, a rich purple color scheme dominates here, giving it a powerful presence both on the shelf and on the lane. Under the hood works the extremely rev-happy Defiant LRG core, which comes with a very low 2.47 RG and a high 0.053 differential (at 15 lbs). This produces one of the earliest revving reactions on the market. This engine is paired with the proven MicroTrax Solid Reactive coverstock. The surface comes rough-sanded out of the box (typically in the 2000-grit range), which signals immediately: this ball wants to dig. It is not a ball for finesse on dry lanes, but a heavy piece of equipment for a lot of oil.
Comparison
Technically, the Purple Gem plays in the absolute heavyweight class. Compared to the original Roto Grip Gem (Yellow/Rubellite/Citrine), it behaves nearly identically: it is extremely early, rolls heavy and controls the midlane like almost no other ball. The difference lies primarily in the looks. Compare it to the later Roto Grip Exotic Gem, however, and the differences become clear: the Exotic uses a pearl cover, gets much more length through the heads and reacts more angular at the breakpoint. The Purple Gem, on the other hand, starts working much earlier and draws a smooth, unstoppable arc. Against a 900 Global Reality, the Purple Gem often feels a tick more aggressive in oil and starts its rotation a bit earlier, which makes it the ultimate solution when even a Reality skids too far.
On the Lanes
This ball has a clear area of use: heavy oil and long patterns. The Roto Grip Purple Gem is the classic "snow tire" in the bag. It absolutely needs oil in the heads so it doesn't burn up its energy before it reaches the pins. On fresh lanes it gives you the necessary confidence that the ball will grab early enough and not slide through the pocket if you throw the ball fast or have a lower rev rate. It blends the pattern from front to back, which means it handles transitions smoothly instead of reacting erratically. Once the lane breaks down (transition) and the heads dry up, though, it should be put away, since it otherwise loses energy and carry (roll-out). It is a pure specialty tool for high volume.