Length: 134mm Width: 134mm GE Watt-Miser 21 Watt 2D 4 Pin (GR10q) compact fluorescent lamp. This energy efficient 2D (PL-Q) lamp has an average life of 12,000 hours and has an A class energy efficiency rating. 2D lamps are available in colours: - Extra Warm White = 827 - Standard White = 835 Actual wattage is 19w This lamp will save you £1.70 per lamp life. GE 2D lamps are the ONLY 2D lamps on the market that are recommended for emergency lighting applications. GE 2D Watt-Miser Lamps deliver market leading lamp life, with execellent energy saving performance that is unique to GE 2D lamps. They provide similar lumen output as standard 2D lamps but provide energy savings of up to 12% dependent on ballast and wattage.. The Watt-Miser 2D\'s are the only A class energy rated 2D lamps on the market and are retrofit to work with existing fittings and ballasts. Please note - These lamps should be replaced like for like. If you have an 21w lamp in your fitting, it must be replaced with an 21w lamp. You cannot reduce or increase the wattage.