The river is full of large round rocks with river water constantly running. Crotch is lined in black cotton. If youre a womens 5. And Im not one of those people who cares *that* much about sound quality. The overall basic first listen to the CF2W (CF2W for short, because I am tired as hell writing it out), is warm, and has a bass tilt as well, very reminiscent of their house sound. they are non slip so she definitely feels secure with these shoes and gained confidence to walk without assistance. Two hour battery life. Beautiful colors, put together well. If someone had given me a set of these a few years ago before the age of bluetoth I would have been really impressed. They certainly arent meant to be worn with smart clothes, but if you are in and out of the house and garden during the summer then they are perfect.