Is the 40-inch measurement the internal or external length

Complete Sealing Kit: Includes brass washers and premium gaskets designed to prevent leaks under consistent steam pressure

The Trane VAL4924 Gas Valve is a 3/4" 24V NG valve designed as the authoritative OEM replacement gas valve for the legacy VAL2521 and the White Rodgers 36C series

allowing your HVAC system to maintain consistent indoor temperatures while significantly reducing energy consumption

This ProTech gas control unit functions as a critical safety and operational component

Siemens Building Technology 331-2904 Actuator 321142-301 Is the 40-inch measurement theThe Siemens 331 2904 is a heavy duty #4 pneumatic damper actuator designed for the gradual or positive actuation of large dampers in commercial ventilating systems. This piston type actuator features an all metal body construction and is specifically UL recognized for high stakes fire and smoke applications. With a 3 7 psi spring range and a generous 4 inch stroke, it provides the necessary force for reliable operation of outdoor air, return air, and