Polyform F-4 Twin Eye Fender 8.5" x 40.5" - BlueF 4 Twin Eye Fender 8. 5" x 40. 5" Blue Polyform has been producing the F Series fender for over 50 years and there is no comparison when it comes to quality, range of sizes, and protection offered. The F Series fender has offered protection to the world's finest yachts and fishing vessels. Why? Because the owners and captains of these prestigious boats know that they can rely on Polyforms F Series fenders to offer the size, strength, and