Parts won’ t shrink or change shape while curing and the urethanes can be used to make precision molds that reproduce fine detail. Flexane 80 is a two-component, medium-viscosity (10,000-cps) urethane that cures to a semirigid (Hardness Shore A 87) rubber that returns to its original shape despite 650% elongation. It pours easily and cures in 10 hr. Flexane 94 cures in 5 hr and produces more rigid molds. Both urethanes come in 1 and 10-lb containers.

Devcon, 30 Endicott St., Danvers, MA 01923, (800) 933-8266,