These filters are offered in MERV 10-15 according to ASHRAE Standard 52.2. Operating face velocities up to 625 fpm are available for all models. Precision Pak filters in depths up to 55.9cm are suited for variable air volume systems. filters with greater depth are not recommended. Precision Pak filters are UL 900 Class 2 listed as a standard and are also available in UL Class 2.5cm both synthetic and glass media.