The 80 series of blue (cooling) colour temperature conversion filters are used for exposing daylight type colour materials under tungsten illumination. The 80b increases the colour temperature from 3400k to 5500k. This 67mm filter is usable with Hitech 67mm holder systems or any 67mm (2.67″) holder. The filter is also available in 85mm, 100mm, 150mm and 165mm sizes. Hitech filters are made from the highest quality 1.5mm optical resin.