Knightsbridge 2 Gang 25mm Galvanised Steel Back Box

The Knightsbridge 2-gang 25mm galvanised steel back box provides the recessed mounting housing for double-width electrical accessories including sockets, switches, dimmers and USB outlets. Pressed from 1mm galvanised steel sheet with a zinc coating for corrosion resistance, the box measures 132mm wide by 73mm high with a 25mm recess depth from the wall surface.

Designed for installation in masonry, stud walls and dry-lining partitions, the box includes one fixed mounting lug and one adjustable mounting lug to accommodate minor variations in stud spacing or plasterboard thickness. The earth terminal accepts a 2.5mm² conductor and provides a bonding point for metal faceplates and accessories. Multiple 20mm diameter knockouts on the sides and rear allow cable entry from any direction, with the unused knockouts remaining closed to prevent plaster ingress during installation.

The 25mm depth is the minimum standard for most UK socket and switch accessories, suitable where wall cavity depth is limited but sufficient space exists for the accessory back-plate and wiring connections. The galvanised finish prevents rust in damp environments including external walls, bathrooms and utility rooms where condensation may occur behind the wall lining. The box is EN 60670 compliant and carries a 25-year warranty against manufacturing defects.

Product Specification Sheet

What accessories fit this back box?

The 2-gang 25mm depth accommodates most UK double-width sockets, switches, dimmers, USB outlets and data plates. Check the accessory manufacturer's specification for minimum back box depth before purchasing — some USB sockets and smart switches require 35mm or 47mm depth.

Can this be used in bathrooms?

Yes. The galvanised steel coating provides corrosion resistance in damp environments including bathrooms, provided the box is installed in a zone permitted by BS 7671 wiring regulations and the final accessory is appropriately rated for the zone.

How are the cable knockouts removed?

The 20mm knockouts are scored into the metal and can be removed by tapping with a screwdriver or using knockout pliers. Remove only the knockouts needed for cable entry — leave unused knockouts in place to prevent plaster or debris entering the box during wall finishing.

What is the adjustable mounting lug used for?

The adjustable lug allows the box to be positioned accurately when stud spacing or plasterboard thickness varies slightly from standard. Loosen the lug, reposition it along the slot, then tighten once the box is aligned correctly in the wall cavity.