Threads into your spark plug hole and acts as a stop for the piston which prevents the engine from turning over

and the test of time

1977 HONDA ATC90

it incorporates full frame protection to below the footpegs

2016 POLARIS RZR 4 900 EPS

VertexWinderosa - Complete Gasket Set with Oil Seals - 811 (8110044) Options:Complete Gasket Set Threads into your spark plugThis set includes all gaskets and oil seals necessary to rebuild the engine and transmission. Dirt ATV (811) sets include all OEM specified gaskets, o rings, and engine oil seals for to rebuild the engine and transmission including output shaft, water pump, clutch, shift and starter seals Includes formed rubber valve cover gaskets Does not include mechanical water pump seal