The Luna G3 CPAP/APAP Replacement Filter Cover is available to order for those patients who have misplaced their filter cover. PRTG301 is the BLACK filter cover which matches the LG3500 and LG3600 Models. If you need a replacement filter cover for our Bilevel Devices, please order the PRTG302, which is the LG3700 and LG3800 Replacement Filter Cover in Ivory.