Dunlop STRAPLOK® Strap Retainers Traditional 

The Dunlop Straplok System is the strap retainer designed with the artist in mind.  It's 360 degree groove and ball design allows the unit to rotate without catching. Case-hardened steel skin guarantees long life.  Interchangeable strap buttons allow the same strap to be used with several guitars.  Release tested up to 800 lbs.  Dunlop Straplok buttons will not come loose under normal playing conditions.