Duolock is a brand name. I believe duolock developed them and people call them that like people call tissues kleenex's. As far as I know they are simply called snaps. I've used then for longer than I can remember. What I like about them besides the ease of lure changes is that you waste less line retying knots. With the new tougher lines I can go quite a while before I need to retie a snap. Over the course of a season it may mean one less reel respooling. I tried the fast snaps once and found they were difficult to use and the design seems like it would pull straight under pressure