There are two common Zenoah twins, the 445 and the GT80. They are the same physical size and differ only in their displacement though they use different cylinders, pistons, etc. The 445 has a plain aluminum intake manifold where the GT80 has a black manifold. The 445 cylinders have no cooling fins on the top of the cylinders where the GT80 has several very small fins in that area. Hope this helps ..... there are other identifying features but those are the main ones.