Type E Medium Centerset Metal Couplers with Metal Gearboxes - Black - O ScaleTwo pair per packagePackage Includes:(4) Each 740 Type "E" "Prototype" Metal Couplers - Medium Centerset Shank(4) Each 818 Metal Gearboxes & lids(5) Each 850 O Scale Centering SpringsThis 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 Metal Gearboxes and lids. The 740 Metal Coupler may be mounted with the included 818 Metal Gearbox or 817 Plastic 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. Use a insulated 817 Gearbox or the 745 Type E Medium Centerset Metal Couplers that includes the insulated 817 Gearbox.New 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...