The silver plated clips snap open so you can loop them into your project to mark your place. I use them to mark the final stitch in a row or to mark places where the pattern changes. They're especially helpful when working in the round and helping you know when you've reached your joining spot and it's time to move up a row.
While I've used the plastic kind for years and rely heavily on them, they're not exactly the prettiest things in the world while these special ones are really going to stand out. They'll make you smile every time you pick up your hook.
The shapes are small and the edges are rounded so they shouldn't snag your yarn. They'll help you stay on track so you spend less time frogging your work!