Stopper. Black Diamond Stoppers are an essential for every trad rack.. Time-tested passive pro, Stoppers are a direct link to the original chocks that started the clean climbing revolution. Designed with a transverse taper that permits sideways placements in flares and shallow seams. Anodized by size, they're quickly identifiable and rounded edges make for easy removal. Each Stopper is equipped with a durable, galvanized steel cable.