Filter Minder® Graduated Air Filter Indicator - Threaded Mount Model No. 135501 (1/8" pipe thread) 136501 (3/8" straight thread o-ring) 137501 (M-10 thread) How Does It Work? The graduated indicator monitors engine air filters. The position indicator progressively fills the window as air filter restriction increases, locking at the highest restriction. The air filter should be changed when the position indicator reaches the red zone. Mounting Mounts directly to air cleaner or air induction piping. Adapter fittings available. Specifications Vacuum Indicator (differential and pressure available) Locking type (non locking avaliable) Operating Temperature: -40 to +250°F (-40 to +121°C) Standard Calibration: 8-35" water vacuum (2-8.7kPa) at the red zone Accuracy: ±10% at red zone Material: Polycarbonate housing Dimensions Length: 70.2 mm Diameter: 50.9 mm   HOME WHAT WE DO HISTORY CAPABILITIES PRODUCTS CONTACT   Engineered Products Co. 2940 Airport Blvd. Waterloo, IA 50703 Ph: (319) 234-0231 Fax: (319) 234-8922 info@filterminder.com