Metolius Astro Nuts are silicon-bronze micro climbing nuts available in five sizes. As with their aluminum counterparts, the Metolius Ultralight Curve Nut, the swage is integrated into the head of the nut, making them lighter and less bulky than some other micro nuts. Astro Nuts and Curve Nuts both feature a unique design with a vertical curve on two sides of their heads. This double curve makes them extremely stable and helps them bite, which keeps them from prematurely popping out. These curves also help Astro Nuts fit securely in irregular rock by sinking in around large crystals. The double curve is slightly offset, making these nuts decent in pin scars, but not wonderful. They are tougher than most micro nuts on the market, making them a good option for free climbing.
Metolius Astro Nuts are our top performers in highly featured rock. The vertical double curve design of Astros gives many advantages, including great bite, which reduces the odds of them popping out. They have good parallel crack performance and two excellent placement options. The double curve also makes them among the most difficult nuts to clean. Astros have tough heads but the cables tend to kink rather easily. Astros are a good choice for free climbers on micro-protected climbs. They have a slightly offset taper that works okay in pin scars, but most aid climbers will prefer DMM Brass Offsets.