Kick start shaft O-Ring set for N/C & W/C 250/350/450cc models. The smaller O-Ring is the correct size that fits in the recessed area of the clutch cover. The larger O-Ring is a additional part that fits between the case O-Ring and the kick starter. The kick starter pushes up against the 2nd additional O-Ring and helps keep it in place and gives it a bit of a squish. Helps on bikes with worn kick start shaft case bushings to keep oil leaks at a minimum.