At DIR diving only wing-style BCD´s are used. The reasons for that are on the one hand, that the diver has no bothersome jacket in front of his body, which is on plus not streamlined at all. On the other hand you can get better a horizontally position than with other kinds of BCD´s. At the surface it is possible (against other sources) to get in a vertical position, to get your head out of the water without any problem. The shape (horseshoe or circle) and size (volume) of the wing itself depends on the used tanks. You can get wings for single tanks from around 12 to 20 liters of lift. For doubles you get wings according to weight and dimension of the used rigg (from around 18 to 32 kilos of lift). At the picture is a horseshoe-style wing with a lift of about 18kg´s which is ideal for large and heavy doubles. At the top the wing is more narrow, becouse it has to leave space for valves and regulators. Furthermore would too much lift at that point lead to too much volume behind your head and due to the buoyancy of the wing it would be impossilble to keep a horizontal position. To get the volume (and buoyancy) to the center of gravity, the wing has more volume at the lower part.
The wing itself is built with an inner bladder and an outer hull, taking for the hull a abraison resistant material to shelter the bladder from longterm stress. The bladder itself is made from a tighter woven material, so it´s more resistant against puncture damages. The zipper from the outer hull is underlayd to give additional protection. You have to take care as well, that water can drain from the hull, when leaving the water, so that there are weep holes at the lower end. Bungy styled wings (trying to reduce not used volume) have to be avoided. They are no better streamlined for they have a uneven surface and if you tare your wing, the gas is pressed out of the bladder. To inflate it orally is more difficult as well and if you try to get out all of the gas of the wing, there might be left some gas between the bungees.
The inflator itself is a standard part which makes it possible to dose the amount of gas gradually for exact buoancy. So called “Power – Inflators” are avoided, for they don´t allow exact dosage and if they freeflow, they will put too fast too much gas in your wing. That will lead to a hazardous situation and will leave you with too little time to react.
The currogated hose is so long, that you can inflate the wing orally, but no longer. So you have nothing dangling around and stay streamlined. It is attached at the top of the wing to make it possible to drain all of the gas. No dump valve is used at the attachment to avoid loss of buoyancy if your inflator gets cought somewhere.
At the left lower end of the wing you find a dump valve, which works as well a overpressure relieve. At horizontal trim this is used to drain gas while pulling the cord upwards (to the surface). If you use a horseshoe-style wing you may need to let gas flow form the right side to the left side or the top to drain that gas. This design makes it possible to adjust your trim when carring stages and allocate lift to the side where it is needed. No ball is used at the end of the dump cord to avoid that the line gets cought somewhere (e.g. between stages) and gas is lost.