[Function] Flat, non-patterned side is the inlet. Raised, patterned side is the outlet. You can blow air into the check valve; the port where air enters is the inlet. [Features] The pipe port of the check valve features a pagoda-shaped slot design for secure fit, providing slip resistance and good airtightness. Made from non-toxic materials, it offers reliable adsorption performance. The non-return check valve is easy to install and allows convenient disassembly for replacement. [Application] Check valve is used in fluid systems to prevent reverse flow, or in pneumatic systems to stop backflow of compressed air. Suitable for use in automotive components, machinery, household appliances, agriculture, and industrial applications. [Material] One-way check valves are constructed for durability, wear resistance, and long-term performance. Opening Pressure: ≤ 0.5 kPa Maximum Back Pressure: ≥ 300 kPa Color: White Material: PVDF Size: Diameter: 1/4 inch (6 mm), Total Length: 1.5 inch (38 mm) Package Contents: 8 x Check Valves Note: Light shooting and different displays may cause slight color variations between the image and actual item. Measurement error allowance is +/- 1-3 cm.