Same as OEM Part# 1122518, 2 1/4" x 1" This filter only fits the Philips Respironics DreamStation Series CPAP and BiPAP machines Replacement Philips Respironics DreamStation Ultra-Fine Disposable Ultra-Fine Filters Replacement Philips Respironics DreamStation Disposable Ultra-Fine Filters. Same quality/lower cost replacement filters. This is only for Philips Respironics Dreamstation.