Black Diamond Micro Stopper-03 - Black Diamond Micro Stopper Rock Climbing Nuts - Stopper Micro Nuts by Black Diamond are the most durable micro nut on the market and a great choice for free climbers who use them a lot. Versatile thin crack pro, trapezoidal Micro Stoppers feature a subtle curve on their longest face for maintaining utility in near-parallel cracks while still catching on crystals and irregularities. A copper/iron mix in the head provides bite in thin placements, while the patented swage is stronger, more flexible and less prone to fraying and each stopper is equipped with a durable, galvanized steel cable. Whether you are a free climber or an aid climber, you will not want to leave home without Stopper Micro Nuts by Black Diamond.
These are much stronger for the size than regular aluminum nuts. They are pretty tough and set nicely. You should really only use the steel stoppers in hard rock like granite, use brass ones on stuff like sandstone.