This Electrostatic Air Filter is a “high” efficiency, Premium Grade air filter that is washable and permanent. It is a “pleated” washable filter with a MERV 8 efficiency rating, and because it is pleated, air resistance is minimized. The electrostatic media pack is enclosed in a heavy duty aluminum frame with drain holes for faster drying after cleaning. The E1S comes in 1″ and 2″ nominal thicknessess and standard and custom sizes. High efficiency (MERV 8), low air resistance, washable and customizable make this the ideal filter for residential and commercial applications.