The bushing, of this connector for a axle, has the size of a 1 x 1 round stone and, like the stone, can be placed on a stud. The 4 horizontal bars make the whole 3 studs wide.
The axle connector with the design ID 68888 does look a lot like this connector, but is only 2/3 high and has no stud holder on the bottom. Therefore, you cannot put that connector on a stud.
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