This is a marvelously effective ball crusher with a very industrial look. Its operation is simple. Every turn of the screw tightens it a little bit more. Once it is on tight the ring at the end of the screw can be used to hang weights from for even more CBT excitement. This crusher is 4.5 inch high and 6 inch wide with an inner opening of 2.75 inch x 2.75 inch. The closure clamps down all the way to zero movement.