What size is 2ba or 0ba when reffering to nuts and washers?

We use this size at work and i would like to buy a socket for it but sockets are sold in mmWhat size is 2ba or 0ba when reffering to nuts and washers?
BA is a british aircraft industry standard (old). You use to be able to buy sockets ranging from 0BA to 8BA.( 0BA is the largest) although actually not that big. I don't think that there is a metric, American or britsh equivelant socket. Some of these sockets can fit loosely but frequent use will damage the nuts or bolt heads.What size is 2ba or 0ba when reffering to nuts and washers?
There is a product called ';GATOR Socket'; one socket fits many different sizes, can be purchased at Walmart or any home supply store