Sections are 40″ (1 meter) long and can be screwed together seamlessly via the threaded connectors. These rails are constructed from high grade 6061 aluminum which is much stronger than the architectural aluminum that is sometimes used for similar applications. The stronger material provides much more rigidity which means a more solid system with very little flex. At 80″ the camera slider rails have less than 1/8″ of flex with a 40 pound load placed at the center. Each piece goes through a 6 step process to make them straight enough and round enough for precision camera movement. 4 sections total (80″ per side) is typical for most setups but you can add as many sections as you need for longer shots. This product can also be used with many other suspended or ground-rail systems that work with a similar OD. The outside diameter is 1.65″ (41.9mm).