The SDI Diagnostics PulmoGuard II PFT Filters are high-efficiency, single-use barrier components engineered to capture aerosol contaminants during pulmonary function testing (PFT). Designed specifically by SDI Diagnostics to eliminate cross-contamination risks, the PulmoGuard II series features a modified housing shape that fits most SDI-brand spirometers and alternative PFT instruments natively without demanding a separate plastic adapter ring.