These couplings have an inside chamfer on both ends for trouble free starting of threads. They have a separate taper to ensure a proper watertight seal and flats on the sides for ease of use with a wrench. Note: All tensile testing results consistently conclude in joint failure due to the elongation of the male threads on the drop/riser pipe. It is therefor recommended that the installer acquire the male pipe thread load capacity data of the drop/riser pipe from the pipe manufacturer. The loads must not exceed either the coupling or drop/riser pipe load capacity. The maximum load bearing weight of the pipe will vary significantly depending on the pipe material. This data is only a guide. The final responsibility for the design of the well lies with the well designer/installer.