This 3/4 size coupler has an extended Trip Pin mounted on a narrow gauge coupler to use with light duty old time equipment. The #711 & #712 works with Kadee's® full size HO-Scale Couplers. With this smaller coupler, gathering will not be as great nor can they bear the same loads as Kadee's® HO Couplers. They should easily handle loads common to the pre-1900 era. This industry leading coupler features a plastic coupler and coil centering spring and comes complete with a insulated draft gearbox and lid. The #712 Magne-Matic® Split Shank Couplers may be body mounted on any flat surface; HO-Scale locomotives or rolling stock.(The #702 Coupler Assembly Fixture can be used to ease assembly) 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. Unassembled KitRust colored 0-48 or 0-80 screws are the most commonly used screws.Screw length will very depending on the mounting situation.Package Includes: (2) Pair Unassembled Split Shank Couplers (2) Pair Unassembled Gearboxes & Lids (5) Each #712 Trip Pins (6) Each #636 Centering Springs (4) Each #402 Self Tapping Screws 0-48 x 1/4" #712 Split Shank Coupler Features: Material - Plastic Shank Length - (3/16") Coupler Offset - Centerset #712 Gearbox Features: Material - Insulated Plastic Dimensions - 27/64"L x 15/64"W x 1/8"H Mounting Specifications: Mounting Height - 11/32" Centerline - 25/64" Trip Pin Height - 1/32" Center Hole - 0-48 Screw. (Screw length will vary) no less then 1/4" length.