This set of casters has 1 1/2 inch wheels, but has the strength to hold a piano! The heavy wheels (one-inch wide) are supported by thick cast-iron holders which are riveted to thick round platforms. The platforms are inserted into the leg of the piano or piece of furniture and then screwed into the wood with three large screws. Each platform is 2 inches round. The stem that inserts into the leg is 7/8 inch long and 3/4 (13/16) inch in diameter. The set is free moving and ready to be used.