THE WATER SOCKS ARE 20 INCHES LONG, ONE SIZE FITS ALL.  NYLON/LYCRA MATERIAL THAT IS 50+UV PROTECTION.  THE SOCKS ALLOW YOUR WET SUIT TO SLID ON AND REDUCE BLISTERS IN YOUR FINS.  WORN ON THE OUTSIDE OF YOUR WET SUIT ADDS TO GREAT VISIBILITY AND IDENTIFICATION BY YOUR BUDDY OR STUDENTS.