This refill solution cartridge is specifically designed for use with the PerfectClean Hearing Aid Cleaning System. (1) replacement cartridge is included with your purchase, and each replacement cartridge should offer about 45 days of use from the date you first install it. Conditions such as humidity, how often you use the PerfectClean, etc. can affect the lifespan of each cartridge. We recommend using PerfectClean 1x/day. When used with the PerfectClean, this gentle but effective solution helps clean, wash, & restore your hearing aids, Airpods, earbuds, ear amplifiers, in-ear monitors, PSAPs, electronic hearing protection or other hearing devices. 100% safe to use with ALL types of hearing aids (including rechargeable), earbuds, in-ear monitors & electronic hearing protection devices. Compatible w/ Oticon, Phonak, Resound, Signia, Widex, Starkey, Lyric, Rexton, MDHearingAid, Audicus, Lively, AirPods, Sony, Samsung, Sennheiser, Bose, and more. Replacement cartridges are required for the continued operation of your PerfectClean Hearing Aid Cleaning System. IMPORTANT: Do not attempt to use other solutions or refill the cartridges with water, etc. or you may damage the PerfectClean and/or your hearing device. Doing so will also void the warranty.