Glasfloss Industries M1124282 Z-Line Series MR-11 MERV 11 Climate Master Geothermal Replacement Filters (case of 6) Increased Media Area, Improved Rigidity, Case of 6 Geothermal Unit Replacement Filters MERV 11 Performance Heavy Duty Moisture-Resistant Construction 100% Synthetic Media Replacement for Climate Master Geothermal Filters - MERV 11 Performance Made in the USA 100-Percent Synthetic Media Heavy Duty Moisture-Resistant Construction