This SoClean 2 filter cartridge and check valve assembly is a replacement for the SoClean 2 CPAP/BIPAP cleaner and sanitizer. The SoClean filter converts activated oxygen back to regular oxygen as it leaves the SoClean 2 sanitizing chamber. The check valve assembly prevents water from your CPAP unit from damaging the SoClean electronics. Despite its name, this SoClean 2 Filter Kit and Check Valve Assembly ONLY includes 1 replacement filter and 1 check valve assembly and does not include 2 of each.