My ninja career started with bombs/cannon balls. 3.5" is the perfect size to start as well. Forget the bar and go with these for your pull ups and single-hand, unilateral- horizontal swings. Great way to build soft-tissue strength and start using those fingertips in a sneaky intro to sloper strength. When my athletes ask me what they should purchase to get started, it is definitely a set of 1.5" rings and a set of 3.5" bombs.