Respiratory - Oxygen Aids - Drive, SportNeb 2 Filter, Pack of 5 : The replacement filter for the Drive Medical Sport Neb 2 is necessary to keep your Sport Neb 2 running at maximum efficiency. Included in the package are 5 replacement filters, keeping your nebulizer running properly and effectively. It is recommended to replace the filter once every 1-2 months, or whenever it appears dirty.