These are commonly used for the suction or low pressure discharge of liquids and are available in a variety of materials. Combination Nipples are not for use with heavy duty/high pressure air, steam, or any critical/harmful applications as they could result in coupling blow-off due to the shape and design of the barbs. The maximum rated working pressure varies with the size, application, construction of the hose, type of clamps used, and with the method of installation. As a general rule, these are not recommended for pressures exceeding 50-75 psi (varies on coupling method and size), and absolutely not recommended for critical applications where failure would result in damage to personnel, property, or the environment.