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For increased stiffness and improved steering precision, tapered head tubes (see image, on left) and forks pair an oversize lower steerer tube (usually 1 1/2-inch, see image, on right) with a standard diameter upper steerer tube (usually 1 1/8-inch). This combination sheds weight compared to straight 1 1/2-inch systems, and adds stability and stiffness when compared to straight 1 1/8-inch systems. The result is a bike that tracks better through corners while allowing for the use of standard stems.
Whether you're looking for the most aero riding position, to sit as upright as possible, or anywhere in between, with Trek's H1, H2 and H3 fits, there's a Madone that's perfect for you.
H1 (see yellow dots on illustration) is Trek's most aggressive, most aero fit, with the lowest handlebar-position options.
H2 (orange dots) is the right fit for most riders. It sports the same handling as the H1 fit, with a slightly taller head tube that puts the handlebars higher.
H3 (red dots) boasts an even taller head tube and higher bars than H2 and a small handling adjustment for even more stability.