Zircon filters have been on high demand Lee has expanded their options and have a separate swatch book and also packs. Cool LED, Warm LED, & LED Correction. Zircon offers longer life for LED lighting and has been shown to retain at least 80% of their effectiveness after as much as eight months of continuous use on LED downlighters. Manufactured using a 180-micron material they are more than double the thickness of a normal lighting filter. They come in rolls of 10ft. x 4ft., and Pre-cut sheets in 24” x 24”.