Motiv HD Plug Hardener (1/2 Gallon) Has proven successful in reactive resin, urethane and polyester bowling balls. Excellent adhesion to all cover stock materials. Extremely crack, chip and impact resistant. Virtually no post-cure shrinkage so you will not have to worry about separation or flat spots. No air bubbles as it allows trapped air to escape before it cures. Drills straight and true without bit chatter or chipping around the rim. Cures in 6-8 hours at recommended temperatures. 3:1 ratio of resin compound to hardener