Some bike racks have a more complicated mechanism with spring loaded pins and some kind of wedge system tightened by a knob at the rear of the rack for easy access. It’s the latter that can have more restrictive requirements on the receiver due to how those engage and interact with the receiver.
Thule is fond of those on some of their bike rack series, such as on mine, which is the newer version of the Subaru OEM Thule one. The OEM/earlier version one is better, btw. It’s what I ordered, and the company I ordered it from sent the new one thinking they were doing me a favor. I would have ordered from Subaru, but, things weren’t really shipping at the time, and I needed it (or so I thought) for my work commute (work from home extended until July now, so, I don’t need it for quite some time).
Both versions use the same knob and wedge tightening system.
