The ultimate 12 size engine for on road competition use. This 3-port version is 'legal' for all 1/10th on road classes in the UK. It will fit many 1/10th off roaders as well! This completely new engine shares very little with its 12TR predecessor and has been designed with one aim in mind – winning!! Just a look at the purposeful and super-smooth carburettor or that stunning machined cylinder head tells you all you need to know about the OS attention to detail.