Rotor Flywheel Nut Washer For Zongshen NC250 NC250S NC300S NC450 KAYO BSE MOTOLAND AVANTIS ENDURO Dirt Bike Secure Fastening Complete flywheel rotor nut plus matching flat washer compatible Fit For Zongshen NC250 NC250S NC300S NC450 engines, For KAYO BSE MOTOLAND AVANTIS enduro dirt bikes tensile nut with thread pitch crankshaft thread for secure flywheel locking Thickened anti-loosening washer evenly distributes tightening pressure to avoid crank thread damage during installation treated surface rust, engine temperature vibration from RPM off-road racing Direct OEM replacement set for stripped, damaged or missing flywheel fasteners during engine rebuild or stator