30 Series Coupler Medium (9/32'')HO Scale 30-Series Plastic Couplers with Gearboxes - Medium (9/32") Underset ShankThis industry leading coupler features plastic standard coupler with metal knuckle, and 621 torsion centering spring and comes complete with 233 insulated draft gearbox and lid. The 37 Magne-Matic® Metal Coupler is designed mostly for body mounting with limited space either above or below the mounting platform, with or without Draft Gear Box Lid and with Draft Gearbox Lid either on top or bottom.Note: The 30-Series Torsion Spring can be mounted either below or above the coupler shank, but must always be mounted between the Coupler Spring Lid and Draft Gearbox.The 147 Whisker® Metal Coupler mounted in a 252 Snap-together Gearbox is equivalent to the 37 Coupler. The Whisker® Coupler mounted in a 252 Snap-together Gear box makes for simple and easy 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.Package Includes:(2) Pair 37 Plastic Shank Couplers - Medium Underset Shank(2) Pair 621 Torsion Centering Spring(2) Pair 233 Gearboxes & Lids(2) Pair 210 Washers(2) Pair 256 - 2-56 Screws(2) 622 Knuckle Springs 37 Plastic Coupler Features:Material - Metal Knuckle, Plastic Coupler ShankShank Length - Medium (9/32") (center hole to back of coupler head)Coupler Offset - UndersetKnuckle Spring - 622Centering System - Standard ShankCentering Spring - 621 Torsion Centering SpringHead - Standard HeadWorks With - 233 draft gearboxes 233 Plastic Draft Gearboxes & Lids Features:Material - Insulated PlasticDimensions - 3/8"L x 5/16"W x 9/64"HWorks With - NO.5®, 58, 20-Series Couplers 37 in a 233 monted on top. Mounting Specifications:Mounting Height - 29/64"Centerline - 25/64"Trip Pin Height - 1/32"Center Hole - 2-56 Insulated Screws are the most commonly used. (Screw length will vary) 37 in a 233 monted on bottom. Mounting Specifications:Mounting Height - 13/32"Centerline - 25/64"Trip Pin Height - 1/32"Center Hole - 2-56 Insulated Screws are the most commonly used. (Screw length will vary)