For secure and reliable fixing of items and fixtures to masonry, concrete, brick, block etc. Requires an 14mm hole for the expansive bolt. M8 thread requires 13mm spanner to tighten expansion nut. Internal eye diameter: 20mm. Requires a 14mm hole for the expansive bolt. NOTE: These expansion bolts are not suitable for works requiring Building Control or Local Authority sign-off such as safety rails, balustrades, load-bearing joists/ wall plates etc.