Spax RA Frame Anchor T-Star Scews Blue 150mm x 7.5 (tub of 100) can be used on wood, stone, and concrete. The countersunk head has a polygonal underside that mills its way into the wood and can therefore be countersunk without having to pre-drill the screw hole. The T-Star guarantees simple and fast work with more efficiency than with other drives. The Spax RA Frame Anchor T-Star are WIROX coated that outdoes conventional galvanisation in both protection & durability.