Has anyone ever used these? I've had two failures using the standard DuoLock snaps in the past and am looking for something without any moving parts (like bending open & closing a snap).. These seem to fit that bill, but I've never used them myself. Thanks for any opinions/comments.

I like them a lot.  I dont use them much anymore but they are the best snaps I have found. 

they work but are hard to put on and off they also have a swivel