The SDI Diagnostics Safe-T-Chek™ One-Way Valve Cardboard Mouthpieces are premium, single-use pulmonary testing accessories engineered specifically for low-risk, asymptomatic expiratory testing. Manufactured by SDI Diagnostics, these specialized mouthpieces incorporate an integrated mechanical valve that serves as an instant barrier against cross-contamination, protecting both the patient population and delicate spirometry hardware.