Cokin P022 80C Color Conversion Filter 3800-5500K (P022).

The 80 series of filters are blue. They are used to balance daylight film under artificial, tungsten or standard (household) incandescent lighting.

80 Series Color Conversion Chart:
80A increases color temperature rom 3200-5500 degrees Kelvin (commonly used with 3200K lamps)
80B increases color temperature from 3400-5500 degrees Kelvin (commonly used with photoflood lamps)
80C increases color temperature from 3800-5500 degrees Kelvin (commonly used with flashbulbs)
80D increases color temperature from 4100-5500 degrees Kelvin (commonly used to remove extreme orange or red)