I climbed the Grand Teton in this shoe, and the rubber stuck well to the rock, and the flexibility made for secure smearing. BUT after a few miles of scrambling, the shoe felt floppy; I couldn't get it tight enough to feel secure, and I got a big blister on the ball of one foot. Also the leathery heal separated from the rubber heal cup; due I think to all of the excess flexing and twisting the shoe went through. Five Ten sent me a replacement pair within a week, but I only use them for day hikes, not as approach shoes. Great for day hikes!