These double riser sections are identical to the ones that come with the master C-stands with turtle base. C-stands get their sizing from the length of their riser sections. The 30” double riser for instance, has two (double riser) telescoping risers and one main section for a total of 90”. Add the height of the base and you arrive at your maximum height, 2 risers, 3 sections (dia.: 35mm, 30mm, 25mm)