The REAL RED Double Arc HPS is 3.5" shorter than traditional 1000W HPS lamps allowing it to fit in much smaller fixtures such as our CONVEX. The Double Arc consists of two 500W HPS arc tubes to provide 1000W of light. This lamp was developed for greenhouse operations wanting high-wattage performance in small, compact fixtures that won't block sunlight. This is a great lamp for light maintenance applications needed to extend the photoperiod for plants.