The AAF 10059.011220 is a 12" × 20" × 1" nested fiberglass air filter, bundled in a case of 24 units. It uses a continuous filament spun glass media held in a one‑piece chipboard frame to guard against corner separation. Rated MERV 1 / MERV 4 for basic filtration, it offers low airflow resistance and is ideal for protecting furnaces and central air systems from large particles like lint and dust. This economical filter design is suitable for residential HVAC systems and is typically replaced on a monthly basis during high‑use seasons to maintain optimal airflow and system efficiency.