Two R/G rally style narrow tanks are replacing the 12cm (5 inch) wider original KTM tank. Also the KTM 790/890 R/G rally tanks are 3kg (6.6 lbs) lighter (fuel empty) and the fuel is moved lower. All this results in significantly better handling of your bike because the center of gravity was pushed further down. You will fit into and turn better in tight spaces. Avoid getting stuck in gnarly terrain!
The fuel capacity is 17 liters (4.5 gal) in both sides together. The tanks are filled independently, but they are connected with fuel line at the bottom. This makes the tanks work exactly the same way as the original, which has 2 compartments as well.