Plasplugs SSCP558 Thermal Block Fixings cuts its own thread in the thermal block to give a superior grip within the 'crumbly' material. For use in: lightweight block, aircrate blockwork, areated blocks, thermelite and colcon.Contains a 8mm drill bit and driver.Recommended Screw Size: No 8 (No 8 to full threaded screw). Plasplugs SSCP558 Thermal Block Fixing (40)