Gravel guards, newer waders have them attached. It allows you to use different boots for various footing, I have a set of felt bottom I use in warm water streams, rubber bottom with studs in cold water if strictly waddling and a set of plain rubber bottoms for in and out of the boat. I have owned both would not want to go back to boot foot, can walk long distance in comfort, gortex breathable is nice in warmer weather, neoprene in cold