-Fitment: Fit for Twin Cam models 1999-Later, Fit for Big Twin 1340 Evo Models 1985-1999, Fit for Sportster models 1986-Later. -Package included: 4x Head Bolt/Nut Covers. -Outside Diameter: 28mm (1 1/8"), Inside Diameter: 15mm (9/16") -They are for the head bolts on either side of the spark plugs. -If you meet any problem about installation and items, please feel free to contact us. Features: Condition:Brand Material:Billet Aluminum Color:Black/Chrome Outside Diameter :Approx.28mm (1 1/8'' ) Inside Diameter : Approx.14.5mm (9/16'' ) Style: CNC Cut Package Include: 4X Head Bolt/Nut Covers Fitment: For All Twin Cam models 1999 2017 For Big Twin 1340 Evo Models 1986 1999 For Sportster Models 1987 2017 Please Ensure This Part Fits For Your Motorcycle Before order