21_1/4x23_1/4x1 Exact MERV 12 Plus Carbon AC Furnace Filters 6 Pack Ventilation/Air Conditioning An exposed temperature sensor allows

An exposed temperature sensor allows for rapid automatic temperature compensated TDS/PPM measurements

high-impact upgrade for any serious grow operation

DERIVED FROM: Ammonium Nitrate

Designed for use with SE (single-ended) lamps only

21_1/4x23_1/4x1 Exact MERV 12 Plus Carbon AC Furnace Filters 6 Pack Ventilation/Air Conditioning An exposed temperature sensor allowsNordic Pure Custom MERV 12 Plus Carbon air filters are made based on the actual measurements so be sure to measure your current filter to get the EXACT dimensions before ordering. As with all Nordic Pure filters, the effective life of your filter depends on the environment in which you live. We recommend changing 1 and 2 filters every 30 90 days. Our 4, 5 and 6 inch thick filters could last up to 6 months. EXACT MEASUREMENT: Furnace and air condition