A modular hose coupler for carrying air or other gas is described including in some embodiments a valve (1) designed to reduce air-hammer effects and improve aerodynamic flow. Some embodiments include self-lubrication. Some embodiments include a secure release ring (2) requiring twisting before release, reducing accidental release in debris-laden industrial environments. Other embodiments include sealing structures (01, 02, 03) designed for exclusion of dirt, robust performance and enhanced lifetime.