Coupler assemblies for OO gauge Ratio 4-Wheel coach kits. Might work for other vehicles too. Designed to work with Bachmann spare couplers like this: https://www.hattons.co.uk/19635/bachmann_branchline_36_027_10_x_mk2_couplings_nem_shaft_cranked_with_pocket/stockdetail.aspx They should also work with any dovetail style NEM pocket (model of one to follow shortly)