Plasplugs® Thermal Block Fixings cut their own thread in the thermal block to give a superior grip within the 'crumbly' material. For use in: lightweight block, aircrete blockwork, aerated blocks, Thermalite and Celcon. The pack contains an 8mm drill bit and driver. Recommended Screw Size: No.10Pack of 40 Plasplugs® SSCP558 Thermal Block Fixings