Separately controlled One or Both - For the Macchil-Castoldi MC72 which still holds the world speed record for piston engine powered seaplanes of 440.681 mph set in 1934 - The exhaust stubs on each engine are Par 65 Centre forks bent to suit the 1/2" x 3/6" Brass flat Exhaust manifolds pitched at 10mm & locked from below by 8 BA x 1/8" grub screws. - Scale - 1/18 (approx) Only 4 parts in each engine are non-Meccano (so far :-) even if others have been "altered"