Bionaire 510 Electret Air Filter.

Bionaire 510 Electret Filter is a Genuine OEM Bionaire Filter.
510 Electret Filter fits Bionaire BT500, BT500S, BT501.
Bionaire 510 Electret Filter traps microscopic dust, allergens, tobacco smoke.
Filter Dimensions, inch. 22.4 x 4.3 x 0.2.
Filter's Lifetime: 3 months on average.
Bionaire 510 Electret Filter comes 1 filter per pack.