☆ This mid column is ONLY used for RT90C heavy duty tripod. ☆ Max load is 66.1lb/30kg, tube diameter is 1.8in/40mm, perfect for carrying long lens. ☆ ER40C is made of genuine 10 layers carbon fiber which is very strong and lightweight, its net weight is only 1.3lb/0.57kg. ☆ It has a 60mm diameter installation pan, compatible with most tripod head. ☆ Interchangeable 1/4”-3/8” screw and the limit groove give you wonderful experience.