With API standard and ISO standard, they are processed by applying corrosion & wear resistant coat on common coupling with special surface treatment technique. Both-way coupling can protect not only coupling but also oil pipe, preventing and reducing abrasion to them. Its wear-resisting performance is larger than normal joint; it is obvious especially under the bad condition, and the service life lasts 10 times than before. The abrasion to the rod is reduced by 3 times after you using this joint. Also, the friction resistance is reduced by 15-35%, saving land electricity waste, increasing the operating safety, decreasing the accident rate.