The SDBA is a type of frogman's rebreather breathing set. Many of the world's navies and army marine corps have used it since 1971.
It is made by Mercury Products (contact information) in Billingshurst in England. The SDBA is described on this page.
The breathing bag is square with rounded corners, on his chest, exposed. Its absorbent canister is cylindrical with flat ends, crosswise on his belly, in a rubber sheath. It has a loop of wide corrugated breathing tubes; one of them originates at each end of the canister; the right tube has a side connection to let gas in and out of the breathing bag as he breathes. It has two long thin oxygen cylinders lengthwise on his back. It can be supplied with a mouthpiece or a fullface mask; the mouthpiece has a valve on its front to close the breathing tubes when the mouthpiece is not in his mouth. Its dive duration is about 3 hours.
It has a nitrox variant called ONBA.