These are 3mm outside dimension jump rings. They are 0.6mm thick. Made of strong stainless steel plated in titanium alloy.
They ae sold all attached to each other. Take them apart one ring at a time as you need them or use it as a chain.
You can also buy them as chain in bulk to use them either way. The chain in bulk is found by clicking here.
Each round link of this chain has an outside diameter of 3mm constucted of 0.6mm wire.