The lamps produced around 30 lumens/watt, which is about double the efficiency of the tungsten incandescent lamp, but less than more modern sources such as metal halide. They had the advantage of no mercury content, convective air cooling, no high pressure rupture risk, and nearly perfect color rendition. Due to low efficiency and competition from more common lamp types, few installations remain today, but where they do, they can be recognized by a characteristic rectangular/elliptical reflector, and crisp blue-white light from a relatively long tubular source.