With Vibram 'Idrogrip' soles, a "breakthrough compound that significantly improves grip on slick surfaces," the boots worked surprisingly well on the pea-gravel and small rocks common in the Beaverkill. I don't know about using rubber-bottom shoes on really slippery bottoms, like the kind found on my favorite stream, the Neversink, or the upstate New York Salmon River. I'll stay away from felt - or, at the least, designate a felt pair solely for use on the Neversink, another pair for the Salmon, and so on. But rubber soles, even first-rate ones like these, make me nervous on slippery rocks, and I'm thinking either studded boots or Corkers might be a better option. But, I'll do some more testing before I make up my mind on this one.