This purchase is for a set of engine case covers for the above models. The bolts are made of the highest grade commercially available 12.9(177,000 psi in tensile strength). The cover is made of UHMW-PE (ultra high molecular weight polyethylene). This UHMW-PE plastic of 15mm thickness will replace the flimsy stock 3mm cover and provide much more protection to the engine case in a low side. Rest assured that you are getting the best material commercially available.