These bases are the thick (I would guess about 5/8 of an inch) rubber type with a waffle like structure underneath to help with stability. I thought they seemed a bit expensive, but after purchasing and using them with my son, I believe the price is justified. These work much better than the flimsy cheap bases which migrate all over the field as they are used. These bases are heavy enough to stay put. It would have been nice to have a Pitchers rubber too, but it isn't like you can push off any non stationary base anyway. Still, it would be nice to have a reference point for the pitcher.