There are a number of different sizes and shapes of locking karabiners available. I have settled on a few of the Wild Country ION screw gates. They are both light and strong.

Features:

Hyperlight, Keylock nose, I Beam back, Hot forged, High gate open strength, High strength thimble. 3 Sigma Rated, UIAA, CE EN 12275, 7075 Alloy. All Wild Country screwgate thimbles are made from high strength 7075 alloy which resists internal pressure to prevent accidental gate opening. All Wild Country screwgate karabiners are ‘proof loaded’ to 10kN and 100% inspected by hand.

Weight (g): 50g
Design: Screwgate
Major Axis Strength (kN): 24
Minor Axis Strength (kN): 7
Open Gate Strength (kN): 9
Gate Opening (mm): 19
Locking Mechanism: Keylock