Looking for an alternative to your stock fuel cell cap or maybe you need a fill cap for that custom oil tank or valve cover you are building? Well, look no further! Holley has created a full line of Billet Fuel Cell Caps and Billet Fill Caps. Holley caps are CNC machined from 6061-T6 billet aluminum and they feature a bright black anodize for great looks and corrosion protection. Each cap features a laser etched Holley Equipped logo so you know it is quality product. Holley Billet Fill Cap kits allow you to put a fill cap or inspection plug anywhere it is needed. Kit #166020ERL is a bolt on with an O-ring seal and features a 2.17" 4-bolt style flange with stainless hardware. The kits has an easy to grip screw on cap with O-ring seal and a 1.38" diameter opening.