This kit is only suitable for the current XTX200 and XTX100 first stages (FSR and FST type). A 5th port offers the user more versatility in terms of hose routings and port positions depending on the type of diving. This particular version incorporates a heat exchanger which acts as an additional safeguard against freezing.
Please be aware that this 5-port kit cannot be used on the old style XTX 1st stages. It has to be one of the current (post-September 2012) XTX200 or XTX100 with the new metallic decal.
5th port allows for a hose routing options that can be advantageous when mounting the first stage to twin cylinders.
Heat exchanger helps resist freezing in cold water.