Description:Conditon: Aftermarket 100% New
Outside Diameter : 28mm (1 1/8")
Inside Diameter : 15mm (9/16")
Material: High Quality Aluminum
Color: Black / Chrome
Package Included: 4x Head Bolt/Nut Covers

They are for the head bolts on either side of the spark plugs.
No Installation Instruction And Installation Remove Easily

Fits for following models?
Fit for Harley-Davidson all Twin Cam models 1999-Later,
All Big Twin 1340 Evo Models 1985-1999,
All Sportster models 1986-Later .