The barrel appears to have a sleve made and glued to the slightly smaller microscope barrel thus making it a telescope eyepiece to fit standard 1.25 eyepiece sockets. It fits all 1.25 sockets I've got as snugly as any normal eyepiece.
Ha! to be honest I don't know I have never actually used it myself as I favor 2" televues in my dobs myself. Its been one of those odds and sods left hanging around after buying job lots which had other stuff I was after. Answer Dunno
