The #142 Kadee Magne-Matic Whisker Coupler features a Metal Coupler, Metal Whisker Centering Spring, insulated Draft Gear Box and Lid. The #141 Coupler may be mounted with supplied 242 draft gear box or with manufactures cast-on coupler pockets. 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. Includes two pair per package.