Injection molded reinforced nylon for strength. Vented to prevent water accumulating in fender tube. Professional "finished" look. Fits 3/8" diameter rope. designed for use on TayloMade® fenders with 3/4" I.D. tubing. May be used on other brands, but due to variation among brands., the consumer must verify a tight enough fit between the tube and product for proper function (center tube must be enough to keep the product halves firmly together).