THIS IS THE HANDLEBAR HOLDER BLACK KNOB THAT HOLDS ON THE BARS TIGHT TO THE TOP CLAMP ON THE Z50A'S K3 THRU 1978. IT IS LONGER THAN THE OLDER Z50 KNOBS. 20G @ *NUT_HOLDER HANDLEBAR_KNOB SOLD_EACH Z50 AND CT70 K0_TO_1978 53143-045-000 7/21M (36F) THIS PART IS NEEDED TO LET THE HANDLEBAR KNOB SCREW INTO TO HOLD THE HANDLEBAR TIGHT. OR SOMETHING LIKE THAT.FITS K0 THRU 78 BIKES. 36F