Apeks WSX Redundant Air Cell. 

Features:

• Apeks WSX Redundant Air Cell The WSX sidemount system now has a redundant option with the release of the new Apeks WSX redundant bladders.
• The bladders are cut to the same dimensions as the WSX-25/45 bladders and are made from the same ultra durable Armoguard material.
• They are designed to be mounted between the harness and bladder and have reversible inflators allowing the primary and backup inflators to be routed on opposite sides.