Best used as a replacement part for Smart Track Rudder Systems. Fair lead is almost 1 inch long and 3/8 inch high. It should accommodate rope as large as 3/16 or 4mm in diameter, but is commonly used with 1/8 inch cordage. Screw holes are 1/8 inch in diameter. Smart Track housings come with 6-32 stainless steel machine screws and nuts. If there is no inside access you could use number six sheet metal screws (that are pointed, and used like wood screws).