Mitsuba type starter motor brush holder. Note this is the heavy duty version with double wires on each brush. Do not confuse with cheaper single wire versions intended for 250/350cc machines.
Used on Honda CB750, CB900, Kawazaki Z900, Z1000, GPZ1100. Fitting list is extensive. Check carefully, picture is of actual part.
ID = 40 mm, OD = 61 mm
Brush size H=13.9, L =12.5, W= 5.9mm