An item generally round in shape and usually having a centrally located hole. It has at least one flat bearing surface. It is made of precious or semi-precious gem (ruby, sapphire and the like), natural or synthetic. It is intended for use in precision instruments, meters, timing devices, clocks, and the like.
synthetic sapphire or ruby, olivehole 0.500 in. min and 0.502 in. max id; 0.119 in. min and 0.120 in. max od; 0.030 in. min and 0.036 in. max lg special features