Black powder coated billet aluminum. The translucent (see-through) polycarbonate window comes with a protective layer to help avoid scratching and discoloring and is sealed with an o-ring. Allows you to check the oil level without disassembly and provides a view into the working clutch. Comes complete with a derby cover gasket. 16-24 Touring 09-24 Trikes 2015(NU)FLHTCUL FLHTK 07-15(NU)Touring Trikes with narrow profile primary cover