Here is a short easy one. Most HPL lamps below are using Ushio product descriptions out of symplicity. Osram and GE make similar lamps to the Ushio ones given. Note: Lamp code as per on this poll might seem hard but once you understand a few things about it, plus general electrical theory it's an easy question. - This is an easy question Hint 1, look at the voltage Voltage and Light Output: The effect of voltage on the light output of a lamp is ±1% voltage over the rated amount stamped on the lamp, gives 3.1/2% more light or Lumens output but decreases the life by 13% and vise a versa. Do not operate quartz Projection lamps at over 110% of their design voltage as rupture might occur. GE Projection, Ibid p 13 If you want to cheat: http://www.ushio.com/ & Www.sylvania.com Hint 2, What's the difference between lamp descriptions as posted of similar lamps? What do you think the differing letters stand for?