Brand New #420 (1/2" pitch) sprocket 38T Accepts #420 (1/2") pitch chain + Free wheel Adapter + Hub Axle adapter (please select size) The Hub is over sized to fit over the shaft The Hub has external threads metric 35x1.25, threads into the free wheel adapter provided The Hub comes with a set screw Shaft Size options: 1/2" 13mm 5/8" 16mm 3/4" 19.5mm 13/16" 21mm 7/8" 23mm 1" 26mm 1 1/16" 27mm 1 1/8" 29mm 1 3/16" 31mm