3D elbow: Its bending radius is 3 times the outer diameter of the pipe. Due to the small bending radius, the fluid may encounter greater resistance when passing through, especially in the case of high flow rate or high viscosity fluid.4D elbow: Its bending radius is 4 times the outer diameter of the pipe. Compared with the 3D elbow, the 4D elbow has less fluid resistance and is suitable for occasions requiring higher fluid flow efficiency.5D elbow: Its bending radius is 5 times the outer diameter of the pipe. The 5D elbow has a larger bending radius, and the resistance encountered by the fluid when passing through is relatively small, and the flow is smoother. It is suitable for scenes requiring higher fluid flow efficiency and lower pressure loss, especially in high pressure or high flow rate pipeline systems.