"These dry linig boxes are great value. Actually I have installed them in wood panelled walls 12mm thick. Same principle though as dry wall or plaster board (whatever you want to call it). I have fitted 18 of these in a cabin / studio for various purposes and they do the job. Easy fitting, nuff said!
I also used these to fit double gang accessory facias (for Studio cabling), and OK the access for the cables was a bit tight, but this is not a normal use for these... For the mains plug sockets they were perfectly fine!"