The 81090 Air Mass Filter corrects the output of a xenon lamp to better match the solar spectrum found outside of earths atmosphere. This 2 inch x 2 inch filter fits into the solar simulators integral filter holder sold separately, or can be mounted into an external filter holder which will flange to the Oriel Research Arc Lamp Housings. The 81090 is an AM 0 type filter to the ASTM E 490 standard.