Meet Fit Grips Sport: spheres that are the same size as a baseball and let you increase the outside diameter of dumbbells and resistance bands. They are made of non-slip military grade silicone and have an ergonomic design. Fit Grips Sport spheres have an outside diameter of 2.5 inches. They could prove useful for MMA fighters, bodybuilders, and everything in between. You can get yours for under $30.