The classic HMS 'biner with its big smooth bottom curve is a popular favorite. Modern climbers have Weighing only 48g., when you want to shave ounces, this is the locking 'biner for you. appropriated this design to use as an all-round harness 'biner because its wide radius bottom curve works smoothly with virtually all belay and rappel devices. The large size is great when you're trying to clip together multiple anchors. Body forged into a slight 'D' shape, resulting in a thinner profile, lighter weight and increased strength.