The #153 "Scale" All Metal Self-Centering WHISKER® Coupler features a "Scale" Metal Coupler (a smaller head coupler which is more to scale and is patterned after the type 'E" couplers) & Metal WHISKER® Centering Spring, insulated Draft Gear Box and Lid. The #153 Coupler may be mounted with the supplied #242 draft gear box, other Kadee® HO-Scale draft gear box shown below or with the Manufacturers cast-on coupler pockets. The coupler will couple and uncouple with other Kadee® HO and HOn3 couplers. The coupler has the same shank length as the #23, 33 or 43 coupler which will allow the modeler to remove the existing #23, 33 or 43 coupler and replace with the new smaller coupler. The #153 coupler is made of the same metal as the #43 for strength and rigidity. 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. The #153 package contains two pair of the new coupler and two pair of the #242 gearboxes, and instructions.