These support rods have complementary 3/8" threads on each end and can thus be screwed together in any combination to extend one another. They can also be attached to the quick release twist-lock of the BF 250 floor stand.
A metal cap is provided to allow covering the upper threads of an STR if desired. It is also possible to attach several RC/RL tubes to one STR bar using several RG 8 tube swivels.