X-Roc was developed for pouring the duplicate model in processing thermoplastic appliances such as: Flexite®, Valplast®, Flex-Star V, TCS®, FRS®, DuraFlex®, & DurAcetal®. This stone compensates for the shrinkage of these materials, thereby eliminating tight fits on removable prosthetics processed with conventional stones. 1.10% Expansion. 22-25 Minute Set Time. 29:100 W/P Ratio. ,000 psi (90 MPa) Compressive Strength.