[Function] Flat,non-patterned side is the inlet.Raised,patterned side is the outlet.You can blow air to the check valve,the port where the gas can be blown is the inlet.[Features] The pipe port of the check valve is designed with a pagoda-shaped card slot, non-slip and non-toxic, with good airtightness and good adsorption percompatible withmance.The non-return check valve is easy to install, convenient compatible with you to unscrew and replace[Application]- Check valve is used in fluid system to prevent reverse flow fluid, or used in pneumatic system to prevent reverse flow of compressed air, can be applied to tomotive parts, machinery industry, household appliances, agriculture, etc.[Material]- The one way check valves are sturdy, wear-resistant and durable compatible with long-term useOpening pressure: less than equal 0.5 KpaMaximum back pressure: greater than equal 300Kpacolour:WhiteMaterial:PVDFsize: Diameter: 1 or 4 inch or 6mm, Total length: 1.5 inch or 38 mmPackage Contents:8 x Check ValvesOnly the above package content, other products are not included.Note: Light shooting and different displays may cse the color of the item in the picture a little different from the real thing. The measurement allowed error is 1-3cm.