This is the Xpand, an expandable pocket for Waterproof suits with WPAD™ – the Waterproof Personal Accessory Dock.

The Accessory Docking System by Waterproof is a simple but ingenious construction, which connects the Xpand Pocket to the suit with a double Velcro fastener. It is easily removable when not in use. The WPAD Xpand Pocket has a D-ring inside and a PK zipper with a stainless steel slider. It can be expanded with another zip.