These inlet and dry box seals are for the PR System One Humidifier
(widely known as the 50 series) and System One 60 series humidifier
by Philips Respironics.
The inlet seal connects your CPAP machine and the humdifier. The dry box seal connects the water chamber and the inlet prevents pesky water from slipping through potentially causing unnecessary unwarranted headaches with a potential defective CPAP machine..