Hardcast Versa-Grip 181 Indoor/Outdoor Fiber Free White. 1 Gallon. Versa-Grip 181 is a premium grade, versatile all purpose, duct sealant for use on all types of metal duct, glass fiber duct board, and flex duct, as well as duct fabric and flexible tubing runouts. Versa-Grip incorporates a built-in fiber reinforcement for exceptional strength, with UV inhibitors for outdoor use. 10 Year Outdoor Warranty when combined with an AFT-701 combination system.