Italian made intake manifolds for a variety of 250-450cc singles. All the manifolds have the regular 53mm bolt hole spacing and take the standard Ducati rubber manifold insulators. Both the 29mm manifolds have a 34.7mm OD where the carb fits on. The 29mm "B" manifold has more bend to it moving the carb away from the frame. The 27mm manifold has a 32mm OD and fits 27mm SSI carbs without a plastic insulator.