I am adding 2 new power sockets to the circuit in my garage. They are metal 2 gang sockets and I am using 2.5mm twin & earth cable. I want to fit glands where the cabling enters the sockets, but haven't used them before and simply need to know the correct fittings. I bought (eBay) a pack of glands coded M12, but these are clearly not correct as they are too small for the 25mm apertures in the sockets. I have checked various suppliers' websites but am not certain from the descriptions which glands are correct. Is it those coded M25? Or M20? Also, is the primary purpose of the glands to prevent dust, moisture, etc. entering the socket, or is it to hold the cable secure, or both of these? Advice greatly appreciated.
presuming it is an attached garage as any work in a detached one is covered by bldg regs.
If so then if wiring is surface clipped simple rubber grommets will suffice.
the knockouts in the boxes are 20mm, you could of course use flex type glands for a slightly better seal but still won't completely seal as oval cable/round gland.
Glands are usually only used with flex or steel wire armoured cable which use a brass gland to earth armouring.