This is a package of disposable filters for Z1/Z2 Travel CPAP Machines. Made from disposable polyester, the filters are designed to be used solely with HDM's Z1/Z2 Travel CPAP machine.
It comes in 2 per pack.
No matter how long you've used them, you don't need to change your filter until it becomes soiled or it appears discolored.
About how long do these filters last before they need to be changed?
The Disposable Filters generally last about a month. The time period is less important than the condition of the filter, though: if it is soiled or discolored after ten days, it will need to be changed. On the flip side, if it's been 45 days and has still retained its white color, you don't need to change it.