3/4 SM‑FS Sub Polished Rod Coupling

7/8 & 3/4 SM FS Sub Polished Rod Couplings are manufactured complying with API Spec 11B. As transition polished rod connectors, they realize size conversion between polished rods and downhole sucker rod strings. Forged from high-quality alloy steel, these Alloy Steel Couplings can be finished with SM wear-resistant coating to produce Sprayed Metal Couplings and improve anti-wear and anti-corrosion performance, ideal for onshore beam pumping wells with water and mildly corrosive fluids. The FS design features wrench flats for easy clamping, installation and disassembly on site, representing typical Wrench Flat Couplings. Precisely machined TPRB internal threads achieve tight engagement, effectively avoiding thread slipping and leakage under alternating reciprocating loads to guarantee reliable long-term operation. The optimized structure maintains sufficient flow area and fits regular casing clearance, widely used in medium and small production wells together with Slimhole Coupl…