A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft.[1] Since each cylinder bank is essentially a straight-6 which is by itself in both primary and secondary balance, a V12 is automatically in primary and secondary balance no matter which V angle is used, and therefore it needs no balance shafts. A four-stroke 12 cylinder engine has an even firing order if cylinders fire every 60° of crankshaft rotation, so a V12 with cylinder banks at a multiples of 60° (60°, 120°, or 180°) will have even firing intervals without using split crankpins. By using split crankpins or just ignoring minor vibrations, any V angle is possible. The 180° configuration is usually referred to as a Flat-twelve engine or even a boxer although it is in reality a 180° V since the pistons can and normally do use shared crankpins.