COMPATIBILITY: Two versions of the PR SystemOne Heated Humidifier were produced by Philips Respironics and each requires a different water chamber lid. If you're using an older 50 SERIES Humidifier choose a CLEAR lid in your shopping cart. If you're using the newer 60 SERIES Humidifier Chamber choose an option with a DARK GRAY lid. If you're uncertain of which chamber lid you require a Universal Chamber Kit (Part 1063785) is available with both lids so you can be certain of getting the right fit.
SYSTEM ONE 50 & 60 SERIES HUMIDIFIER DIFFERENCES: The newer 60 SERIES SystemOne Heated Humidifier includes the words "SYSTEM ONE" embossed on the top of the humidifier unit and have dark gray side panels; older 50 SERIES Heated Humidifiers did not include any wording on the humidifier unit and have light gray (ivory) colord side panels.