The 555-210, Kirby Morgan Restrictor Adapter should be used when an inflation hose is attached to the side block when drysuit diving. The main purpose of the Restrictor Adapter is to limit gas flow in the event the hose ruptures or is severed, and to ensure the loss of supply would not be great enough to significantly affect the diver’s breathing at moderate to heavy work rates. It also helps prevent filling the dry suit too rapidly.