Killark GRK-RG - Cover o-ring, Nitrile (BUNA-N) material. The GR series rectangular boxes with screw covers are for use in locations that are hazardous, corrosive, wet, hose down, dust, dirty, under both sever hot and cold ambient conditions. Cover options; blank flat, lens and domes. The GR series is UL / CSA certified for Class I Groups BCD, Class I Zone 1 & 2 IIB+H2, Class II Groups EFG, Class III, Type 4 & 4X. Also, ATEX, IEC Ex, Ex d IIB+H2 Ex tD A21 IP66 when ordered with suffix “CEN”. The GRs are made of cast copper-free aluminum (less than 4/10 of 1%, supplied standard with a Nitrile (BUNA-N) O-Ring, cast on mounting lugs. The boxes can be pre-drilled internally for factory or field installed mounting pans. Options include, control operators, NPT conduit openings & metric gland openings. - For use with GRK Series fittings.