The 3403 and 3405 are valves created to allow for station transfer on multi-station pneumatic systems. The 3403 / 3405 allow for pneumatic controls to leverage the functionality of various valves to switch the flow and transfer control to a different station. 

The 3403 / 3405 valves are constructed entirely of bronze & stainless steel, and are available in 1/4" NPT and a 1/2" NPT respectively. The photo shown is of a 3403.