7.5 x 42-212 cement screws Cement screw is a kind of expansion screw used for fixing window frame. It wins the trust of customers with the idea of quality first and reputation. This product is produced with C1022 wire, after carburizing heat treatment, surface hardness min450HV0.3, core hardness 270-390hv10, cutting depth (e-f) X0.42, minimum electroplating thickness 3um.