< 3/4 of an inch to small to even fit a 2.5" drive. I vaguely recall < seeing something about 1.8" drives? Am I hallucinating here or does suc < a creature exist? Even smaller...HP made a 1.3" disk drive, Hawkeye ???, I think it was either 20MB or 40MB capacity. The components were so small you needed watchmaker tools to take the drive apart. Jack Peacock