Flush mounted electricity meter box in glass fibre reinforced polyester Will fit all types of Electricity Meter Robust: Reinforced design Back mounting board included Weather resistant glass reinforced fire retardant polyester moulding compound (GRP) Class II BS 476. Quality Standard. BS EN ISO 9002 The new deeper design of box permits the installation of both standard and prepayment meters without the need for any modifications to the door. Another standard feature is the use of a special fire retardant (Class II, BS 476) moulding compound in all of our meter boxes.