8.7mm Serenity

Performance: We refer to ropes as “buttery” when they’re lightweight, supple, and easy to clip, and the Serenity embodied this. One guide tester chose this cord over his 12 others time and time again. It’s the thinnest and lightest (51 g/m, so 6.8 lbs. for 60 meters) single rope that our testers have climbed on; they used it at crags like American Fork, Utah, and alpine-heaven Mt. Whitney in California, where they praised it for not adding considerable weight to already-overloaded packs. One tester was hesitant about the diameter at first, but he quickly gained confidence after watching the rope rake over granite, sandstone, and rough limestone with no signs of wear or fuzz. Mammut’s Coating finish protected from abrasion, moisture, and dirt, which is the true rope killer.
Drawback: It’s not technically approved for use in some belay devices, including the Petzl Grigri 2 (designed only for ropes from 8.9 to 11mm), but testers found that the Grigri 2 still bit down on the cord, with no slippage during belaying, taking, or falling. Still, the belayer should be attentive at all times. Bonus: This rope is certified as a half and twin rope, too.