The 80 series of filters are blue. They are used to balance daylight film under artificial, tungsten or standard (household) incandescent lighting.
Hitech resin filters are made from lightweight, optical resin. These particular Hitech filters measure 85 x 85mm and fit Hitech's 85mm filter holder. They will also fit the Cokin "P" series holder.
Filter factor 4 (+2 stop)
80 Series Color Conversion Chart
80A increases color temperature from 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)