This lockable triple-sealed aluminium recessed manhole cover from EcoGrid is manufactured from extruded aluminium with a 3mm galvanized steel bottom plate and a reinforcement mesh in the cover. Tested to EN124 to lorry load bearing, this recessed and locked manhole cover has three seals. There are two EPDM seals are the base and the third seal is a T rubber seal on the outside frame. The third seal reduces tension between the recessed cover and the frame, it prevents dirt building up and it contributes to the manhole cover being odour-proof, waterproof and gas-proof. Please note: Manhole cover measurements are taken from the clear opening, the internal dimensions of the hole are taken to give the size manhole cover that is needed. This triple-sealed recessed manhole cover is 450mm x 450mm and comes with specialist lifting keys provided by EcoGrid so that fitting and maintenance is easier. Triple-sealed aluminium recessed manhole covers are available from 150mm x 150mm to 1000mm x 1000mm in 41mm and 61mm in-tray depths. For external use, this recessed manhole cover can improve the aesthetics of an area by allowing the manhole to blend as seamlessly as possible with the surrounding area. Instead of a large silver cover blemishing the landscape, the recessed frame is filled with the same substrate as its surroundings and the cover is hidden. This EcoGrid manhole cover can be used on tiled, paved and grassy surfaces. EcoGrid Manhole Cover Specifications Clear Opening Dimensions: 450mm x 450mmExternal Size: 540mm x 540mmIn-tray Depth: 41mmOverall Depth: 60mm