This12 mm Wall Anchor Fasteners is a heavy duty self-tapping concrete anchor that cuts a thread directly into pre-drilled pilot holes. With these fasteners, you don’t have to use any anchor or plug separately. Just drill a pilot hole and use a socket wrench or spanner to tighten the screw into concrete or natural stone or perforated bricks. Features: Rust-Proof Easy Fix Ideal with Many Surfaces.