Nite Ize, believes no product is too small or basic to be improved.
The classic utility carabiner. 
Innovative slide-to-lock feature that securely locks the gate with a simple push and slide movement, and unlocks when you want it to just as easily.
A cross sectioned, rectangular stainless steel body that's durable, low profile, and slim; it feeds more easily through smaller openings and rests flat
in pockets.
Available in sizes:
#6 (to tackle the largest items),
#4 (perfect for attaching to a belt loop or
backpack to carry larger items),
#3, and #2 (for carrying smaller items like keys, and attaching to zipper pulls).