I washed them, but some sand is still trapped and won't come out. Used about 10 times. Repaired sole on the right toe. Below is the manufacturer's description: --------------------- Developed through repeated testing, these sandals use "Non-skid Rubber." They are lightweight and compact wading sandals for upstream fishing. They boast excellent grip performance even without studs in upstream areas with little moss or slime, and significantly reduce weight increase when entering the water. They excel in flexibility, providing a feeling of wrapping around the stones, making them ideal for fishing while walking in the river. The narrower than usual width (2E) and natural rubber toe provide good grip on rocks, and the PVC tape on the heel securely holds the foot. They offer stability beyond that of ordinary sandals. The upper uses 3D Russell mesh, and the design has been carefully researched to prevent small stones from entering. They can also be used as water shoes or deck shoes.