I ordered a bunch to put on the strings of some cloth masks. They work so much better than trying to tie both straps behind your head.
These work better than the original Arcteryx cordlocks on my backpack.
Using these to make stuff sacks, 550 cord with the core removed fits like a glove. No metal to rust and they hold cord just as tight.
I haven't put these into use yet, but they feel like a quality piece of hardware. Relatively stiff action which, hopefully, means they will remain effective over time.
Used these on the ends of a draw cord on a top quilt design. Lightweight and durable. I love that there are no metal bits to rust away.