DUOBLOCK forged wheels are pretty much manufactured the same as the Monoblock forged wheels except that they are mashiened out of 2 separate pieces which are then bolted together. A DUOBLOCK in this configuration pretty much looks like a Monoblock Wheel but with exposed Hardware (showing Bolts) If you do not want the bolts to be seen it is also possible to make them with non exposed hardware so the bolts will not be visible. So there is no lip! Now the question is, why a DUOBLOCK? Mostly because with a DUOBLOCK in some applications you can run a more concave profile. On some applications, not on all applications. Its also easier to have 2 tone finishes.