This Rosco ThermaShield Filter 48 x 48" is a neutral material used in high-heat situations in conjunction with another primary filter (ex. Cinegel) to prevent damage of the primary filter. ThermaShield's vacuum deposited, multi-layered coating, reflects the infrared energy that destroys color filters.
Rosco advises against sandwiching the filters, recommending mounting each in its own filter frame with an air space in between. ThermaShield filters are especially useful on remote fixtures where regular maintenance is inconvenient.