Replacement nasal cushion for the ResMed AirFit N20 Nasal CPAP Mask and the AirFit N20 Nasal CPAP Mask. Replacing CPAP Nasal cushion frequently can assist in eliminating residue buildup that cause infections. So, replace your CPAP Nasal Cushion for the ResMed AirFit N20 Nasal CPAP Mask at least every 30 days to protect your health.