Made by Perewitz. These used rocker boxes are three piece made from billet aluminum. The chrome is going bad now as these are over ten years old. Evolution Rocker boxes are interchangeable for most years with head breather design, even fitting on Sportster Evolution models. No longer available from Perewitz, so hard to find. They use regular base gaskets, but a custom seal (o-ring style) is used also. Sometimes silicone sealer is applied. The hardware is included in the bag. They accept all Evolution style rockers..