There may be other variables on some. For example, I recently had some same size phoenix connectors that I tried to use for an amplifier that a client owned and the previous company did not leave all of them in. I found some in my stash but they had a plastic guide on the bottom and they wouldnt fit in the amp because of this. I guess I could have tried to trim it off but it was the first time I recall seeing something like that so I kept them intact.