The #118 Kadee® Magne-Matic® Coupler features a Metal Coupler, insulated #242 Draft Gear Box and Lid with center screw holes for mounting. Shelfs actually work. The #118 Coupler may be mounted with supplied #242 draft gear box or with manufactures cast-on coupler pockets. Two pair per package Manual uncoupling requires the #241 Dual Tool. The "SF" Shelf Coupler can be easily modified to look like the type "F" Shelf Coupler or "H" Passenger Car Coupler. It is not recommended to use a metal coupler directly on a metal surface or in a metal draft gear box to avoid the possible electrical crossover or shorting that may cause damage. Use the provided insulated draft gear box .