These are the ideal way to convert to Kadee-type couplers (use #747-series Underset Coupler
) for O scale 3-rail trains, by adapting the coupler to the truck. This provides a prototypical buffering action, and attaches with a single screw, with no coupler box cover needed. The spring goes in front of the screw lug, and the only way to convert to scale couplers and keep those tight radius curves. More info here: http://ogrforum.ogaugerr.com/topic/want-to-convert-to-kadee-s-but-have-tight-curves
Guaranteed no mark up.
Updated 18 Nov 2016.