The Glasfloss Puracell II M & MH Series is designed for use in applications where a high degree of efficiency is required in a 4" filter. The Puracell II M & MH Series combines state-of-the-art mini-pleat construction techniques with superior reliability for commercial and industrial applications. The filters feature heavy-duty metal frames in 60-65%, 80-85% and 90-95% ASHRAE efficiencies in header or box style..