OK I get the sales man's defense of their inventory , Maybe offer the consumer the options to make their own Pick
Industrial High Pressure air hose quick coupler based hitch Bike Friday uses for their suitcase Trailer works OK , Too..
I used the Connectors in their Original setting.. Air turbine Motor grinder in shipyard & Big compressor in the Bottom of the Dry dock .
Aosom is where The $100 eBay trailers come from . Their Hitch
Bike Trailer Universal Hitch Coupler
people already have trouble using them on many bike configurations. (As Read on these Pages)
I use the Ball hitch with my Brompton towed Carry Freedom City trailer the rear wheel under fold is unimpeded by having the trailer attached ..
the typical Fold-in-half Bike , You have to take the trailer off anyhow.