My 1UP has the binding-friction system too; there is a large ball in the shaft and you turn an Allen wrench to tighten it and it forces the ball out and thus makes the rack sit eccentrically in the receiver. It seems tight.... But I am never sure how tight I need to make it. Makes me wonder if I might break something if I over-tighten it. I don't know why mine doesn't use a pin.... Maybe only the 1.25" shafts use the pin? Mine is a 2-inch. Probably a moot point; my receiver has just enough room for the 4-inch minimum insertion and almost nothing more, because the spare tire well is beyond. That's all the room there is and if my rack had a hole for a pin, chances are it would be in the wrong place anyway.