COMPATIBLE & WITH VARIOUS SLEEP EQUIPMENT MACHINES: Fits All For M Series, PR System One Series, SleepEasy Machine! Each filter to fit your machine precisely. PREMIUM QUALITY CLEANFLOW TECHNOLGY:The reusable black foam filter is to block large particulate matter, the white ultra fine filter is to block fine particles. Use them together to provide the cleanest air. KEEP YOUR MACHINE RUNNING LONGER AND MORE EFFICIENTLY:Not Only Do Our Filters Help Keep Your Lungs Clean, But It Also Prevents Dust, Dirt, and Other Buildups from Entering Your Motor. 50 PCS ECONOMICAL SET:Include 25 Pcs Reusable Black Foam Filters and 25 Pcs White Ultra Fine Filters, replace your filter every two weeks is recommended. But if you are in a particularly dirty or dusty environment, you may choose to replace your filters more often. This one set full satisfy at least one year needs. Name:CPAP Filters Type: For CPAP Filters Colour:White + Black Material:Sponge Size:4.5x2.3cm/4.5 x 2.5cm Package Contents: 50 * filter cotton Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.