4.8mm self-drilling screws with twin-threaded shank and wafer head. Manufactured by Rapierstar using Zinc passivated carbon steel, for strong, long-lasting PVCU window frame-to-frame, and frame-to-baypole connections. The flat underside of the wide wafer head, prevents the creasing that can weaken the frame, and cause pooling of water, which results in corrosion. Whilst the advanced drill point eliminates the need to pre-drill, and is effective on single-wall and multi-chamber profiles, with or without steel reinforcement.