You need a carabiner for your keys or bag. That just is what it is… But do you want one specific to that function or do you want one that will also hold some real weight in a pinch? If the latter, this is the carabiner you need. It’s cheap, light, and has an axis strength of something like 5,000 pounds.
I’m a carabiner on my keychain kind of guy – always have been. When I get out of my truck, I clip the keys on my belt loop and I always know where they are. It just works for me.
Given that, I’ve gone through all sorts of carabiners for key usage. I’ve been using a Handgrey for about three years now and while expensive as hell, they are the best I’ve ever found.