The nite ize slidelock carabiner has a 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. The rectangular stainless steel body is low profile, and slim it feeds more easily through smaller openings and rests flat in pockets. Size 4 would be perfect for attaching to a belt loop or backpack to carry slightly larger items like bottles.size 4durable stainless steel locking utility carabinersecure stainless steel wire gate with a slide to lock featurealso available in stainless steeldimensions 2.0 x 3.1 x 0.1 52.0mm x 78.5mm x 3.0mmweight 1.1oz 31.00gweight rating 75lb 34kgwarning not for use where disengagement could result in bodily injury or property damage. Not for climbing.