Initially, I just purchased online, but ordered the wrong part. I called and talked to a real person, who helped me order the correct part and offered a reasonably priced return shipping label. That was a welcome change from other recent online purchase interactions.
5 Pack 3/4" Brass Compression Sleeve
Use these 3/4" brass compression sleeves with copper, aluminum, and thermoplastic tubing. Not recommended for steel tubing. Manufactured for low and medium pressure tubing connection work where excessive vibration or tube movement is not involved. Not recommended for application using gaseous media.
Features
• (5) 3/4" compression sleeves
• Temperature range: -65°F to +250°F (-53°C to +121°C)
• Tolerance: +/- .02
• Meets specifications and standards of ASA, ASME, and SAE
• Contains lead

