The Petzl AM'D Ball-lock Carabiner is a d-shaped connetor for devices on harnesses. The shape and size of this carabiner makes it great for most uses, from connecting a belay device to your harness or as a connector at the end of a lanyard. The D-shape makes it one of the strongest and lightest locking carabiners Petzl makes. This model has an auto-locking BALL-LOCK system. Perfectly suited for use with belay devices due to its symmetric shape on both ends of the carabiner.