... API 11B sucker rod couplings, including Spray Metal coupling, class T coupling, Altra High Strength,Sub OD coupling, with various spec ... abrasion-proof, wear-proof and lessening friction coat. It can’t only protect itself but also the rod, preventing and slowing ... proof, corrosion-resisting and reducing the friction.Main Production: CLASS T or CLASS SM WELCOME TO CONTACT ME FOR FURTHER INFORMATION ...