The Austri-Alpin Non-Locking Steel Oval Carabiner - Snaplink - offers optimum durability and strength. This carabiner is patterned on the original U.S. Army Mountaineering Snaplink. Steel is the best choice for severe duty use as it stands up to heavy uses without material degradation. This is recommended for rescue, ropes course and gym use. Non-locking black oxide Army style steel carabiner/ snap link is used for climbing, mountaineering and some rappelling applications. This plain oval style is multifunctional for attaching tactical gear. Carabiners come in four characteristic shapes: Oval: Symmetric. Most basic and utilitarian. Smooth regular curves are gentle on equipment and allow easy repositioning of loads. Their greatest disadvantage is that a load is shared equally on both the strong solid spine and the weaker gated axis. D: Asymmetric shape transfers the majority of their load onto the spine, the carabiner's strongest axis. Offset-D: Variant of a D with a greater asymmetry, allowing for a wider gate opening. Pear/HMS: Specialized oversized offset-D's used in belaying. These are usually the heaviest carabiners.