1.375 tube with .058 wall
.058 is used so they are easier to get on, at least that's what I know some people were doing. I had bars that had a .058 wall thickness and they lasted me a year, worked perfectly.
.058 wall, 1-1/4th inch ID, 1 3/8th inch OD.
bar size is 7/8ths inch. or something close to that