Extensive compatibility: Attic Spreader Hinge Arms Compatible with Werner Attic Ladders, including Models Mk 1 thru Mk 3, A2208 A2210 A2508 A2510 W2208 W2210 W2508 W2510 WH2208 WH2210 WH2508 WH2510 WH3008 WH3010. Note: Only applicable to models manufactured before February 2006. Upgrade design: Upgrade the attic ladder hinge arms with electrophoretic coating technology.The three-layer galvanizing process guarantees excellent wear and corrosion resistance. The ladder spring is made of high quality steel wire, reinforced by special treatment, durable, not easy to oxidize and change color.