Oxballs Bullballs-2 Silicone Ball Stretcher is half an inch taller than the Bullballs-1. These ball stretchers are made from pure platinum silicone, and just like all Oxballs toys, the Bullballs-2 is super stretchy and warms to your body temperature and feels just like a second skin. If youre feeling particularly brave, try stacking two or three Bullballs for added ball stretching! Oxballs products are safe to use with water based lubricants and silicone based lubes. However, do not use any product with petroleum, as it will deteriorate the material. The inside diameter is approximately 2 inches wide to ensure it doesn't interfere during sexual activity but still looks great.