I own a set of the Pachmayr flush mount swivels and bases, but haven't put them on a gun yet. I've never seen them on a gun, but they look kind of neat. I don't know what is done on the front end, but the back looks pretty neat. I bought them to put on a custom rifle that already has flush mounts, but the part that goes on the sling was missing. Unfortunately, they missed being compatible by a little. However, if you buy the Pachmayr set, you have both compatible ends.