Premium 3 / 4 inch straight copper couplings with sweat joint design secure leak proof HVAC connection, featuring oxygen without copper construction for best thermal conductivity and erosion resistance Ideal for sweat soldering copper tubing in split units, heat pumps installations, chill water pipelines, and industrial refrigeration maintenance applications Each set includes 4 identical copper pipe adapters meeting ASTM B280 standards, designed for permanent erosion resistant joints in pressurized HVAC / R systems up to 400 Accuracy engineered with 19mm inner diameter and 0.9mm wall thickness, these polishes copper fittings burrs for smooth installation in air conditioning and refrigeration systems Essential for HVAC technicians and plumbing professional requiring strong, maintenance without copper pipe connection in commercial / residential climate control projects