Type E Medium Centreset Shank MetalThis industry leading coupler features New Generation AAR Type "E" "Prototype" Head Medium Centerset Metal Couplers, and 850 O Scale centering spring and comes complete with Plastic Gearboxes and lids. The 745 Metal Coupler may be mounted with the included 817 Plastic Gearbox or 818 Metal Gearbox (sold seperatly), 819 Extended Metal Gearbox (sold seperatly).It is not recommended to use a metal coupler directly on a metal surface or in a metal draft gearbox to avoid possible electrical crossover and shorting that may cause damage.Two pair per packageNew Generation AAR Type "E" "Prototype" Head:Simple Drop in DesignTrouble Free OperationHidden Knuckle SpringAAR Type "E" Coupler StyleCompatible with Kadee® O-Scale CouplersWorld-Renowned Quality & PerformanceThey just Last & Last & Last...Package Includes:(4) Each 745 Type "E" "Prototype" Metal Couplers - Medium Centerset Shank(4) Each 817 Plastic Gearboxes & lids(5) Each 850 O Scale Centering Springs