As header really. I have a few 70w metal halide discharge floodlights. The covers are clear plastic, possibly polycarbonate similar to those used on cars. Covers are moulded so replacement with clear glass is not an option. These are now rather foggy and hindering the light output considerably.
As my stock of lamps dwindles I intend to replace these with led luminaires, but I have enough lamps to last perhaps a couple of years. Thanks, Nick.