The #118 Kadee Magne-Matic Coupler features a Metal Coupler, Whisker centering Spring, insulated #232 Draft Gear Box and Lid with side and center screw holes for mounting. The #118 Coupler may be mounted with supplied #232 draft gear box or with manufactures cast-on coupler pockets. 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 . Two pair per package.