The Superlec 442KB Galvanised Adaptable Knockout Box is used to extend or repair electrical circuits. 
The main features of the 442KB are: 
3 Optional 20mm knockouts per side 
Manufactured from 1.2mm pre galv steel 
Comes complete with flanged cover and 4 fixing screws 
BS EN 50142 & 3 
Dimensions: (H) 100mm x (W) 100mm x (D) 50mm