Polyform NF-4 Heavy Duty Twin Eye Fender 6.4" X 21.6" - White [NF-4 WHITE]NF 4 Heavy Duty Twin Eye Fender 6. 4" x 21. 6" White The NF Series Boat Fender, one of Polyform's newest innovations, features multiple ribbed, reinforced ropeholds, making it the strongest fender in its class. The NF Series is an extra tough, recreational boating fender and a good choice for use in boat locks and tidal areas where fenders are exposed to high stress situations. The NF Series is designed to last and stand up in the toughest conditions