SST What is it? Size Specific Tubing Important aspect to your bicycle
What that means? Small bicycle smaller diameter tubes, bigger bicycle bigger diameter tubes. This will allow a small frame to have the same ride characteristics as the medium and large frame. If your frame has the same size tubing for a xtra small as a xtra large the small will have a harsh overly stiff and heavy ride and the XL will be too flexible and not strong enough. It costs manufacturers much more money to use size specific tubing but it is very important for ride characteristics. Companies that do: Jamis (even there chromoly steel and low end bicycles!), Salsa, Moots companies that have very limited tubing differences Giant and Trek.