This is the R3 replacement water chamber for Respironics M series humidifiers. If your current humidifier requires a black latch, this is the humidifier chamber lid for you.
This water chamber is not compatible with Respironics PR System One Heated Humidifiers.
How do I tell whether I need the R2 or R3?
Check your humidifier. On the dial, under the number five, there will be a thin line that indicates that you need an R3. If there's no line, you have the R2.
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