This is the Apeks WTX Wing Single Tank 18lb, 30lb or 40lb Options

Features:

• Single Cylinder Wings, Referred-to-As Donuts"
• Oval Shaped Air Cells or Bladders
• Not Permanently Attached to Harness
• Popular w/Technical & Recreational Diving Communities
• Streamlined and Stable Underwater
• No Dramatic Shift of Air from Left to Right
• Smart Design: Allows Cylinder to Nest Deep-Inside-Wing
• Mates Up Nicely to APEKS WTX Collection Harnesses, Plates and Accessories
• Can-Be-Configured in Multiple Ways to Match Your Type of Diving
• Built from Finest Quality Materials
• Designed by APEKS and Built in Their Own Factory
• Drainage: Central Mesh Panel 2 Grommet
• High-Efficiency Drains to Drain Water Quickly
• Access Zipper Located on Front Side to Prevent Abrasion

The WTX and WTX-D Series is a selection of harnesses, buoyancy cells and accessories which offer unparalleled versatility due to the modular nature of the whole system. Each component can be configured into a highly technical rig for those trained to push the limits, or scaled down to make a travel friendly set up suitable for any diver.
Single cylinder wings, often referred to as donuts, are oval shaped air cells or bladders that are not permanently attached to a harness. While single cylinder wings have their origins in the realm of technical diving, they are becoming very popular in the recreational community. Not only are these single cylinder wings streamlined, but due to their shape being a continuous loop, they are very stable underwater. There is no dramatic shift of air from left to right.