PU Straight Pneumatic Fittings Kit – PU4 / PU6 / PU8 / PU14 Quick Release Connectors for 4–10mm Hose

PU-series straight push-to-connect pneumatic fittings (also called union connectors or inline connectors) join two tubes of the same diameter end-to-end — used for extending tube runs, repairing cut tubing, and creating inline connections in pneumatic and fluid circuits. This boxed kit provides an assortment of the four most common sizes (PU4, PU6, PU8, PU14) for 4mm, 6mm, 8mm, and 10mm OD tubing, covering the full range of standard pneumatic circuit tube sizes in a single organized package.

PU Series Naming Convention

• PU = Push-in Union (straight inline connector, same diameter both ends)
• Number = Tubing OD in mm: PU4 = 4mm, PU6 = 6mm, PU8 = 8mm, PU14 = 10mm
• Note: PU14 accepts 10mm OD tubing despite the “14” designation — this is a manufacturer-specific internal code. Always verify the actual tubing OD compatibility in the product description.

Key Specifications

• Fitting Type: Straight union (push-to-connect, both ends same diameter)
• Body Material: POM (acetal) or PA66 nylon
• Seal: Internal collet + O-ring (push-to-connect with release collar)
• Tubing Compatibility: Nylon (PA), polyurethane (PU), polyethylene (PE) rigid OD tubing
• Working Pressure: 0–1.0 MPa (0–145 PSI)
• Temperature Range: 0°C to +60°C
• Media: Compressed air, water, light non-corrosive fluids
• Quantity: 23, 60, 80, or 100 pieces (select above)

PU Union vs PZA Reducing Union vs PE Tee

• PU (straight union, this product): Joins two tubes of the same diameter inline. Use for extending runs or repairing cuts.
• PZA (reducing union): Joins two tubes of different diameters inline. Use when transitioning between tube sizes in a straight run.
• PE (equal tee): 3-way fitting, all ports same diameter. Use for branching a single supply line into two equal branches.
• PEG (reducing tee): 3-way fitting, two large ports + one small branch. Use for branching a smaller line off a larger main supply.

What Questions Does This Product Answer?

• "Can I use PU fittings to repair a cut pneumatic tube?" — Yes. Cut the tube cleanly at both sides of the damage, insert both ends into the PU union, and the circuit is restored. Ensure both cut ends are square — angled cuts reduce the O-ring contact area and cause leaks.
• "What is the maximum pressure for PU push-to-connect fittings?" — 1.0 MPa (145 PSI). For higher pressures, use metal body push-to-connect fittings (SMC, Festo, Parker) rated to 1.5–2.0 MPa.
• "Can I use PU fittings for vacuum circuits?" — Yes, down to approximately -0.09 MPa (-90 kPa). Ensure tube ends are fully inserted and square for a leak-free vacuum seal.
• "How do I release the tube from a PU fitting?" — Press the release collar (blue or grey ring) firmly inward toward the fitting body while simultaneously pulling the tube straight out. Do not pull at an angle — this jams the collet and can damage the tube OD.

Typical Applications

• Pneumatic automation: Inline tube extensions, circuit repairs, tube routing changes
• CNC & machining: Coolant mist system tube joins, air blow-off circuit extensions
• Aquariums & hydroponics: Air line extensions, CO₂ line repairs, nutrient solution circuit joins
• 3D printing: Bowden tube extensions, cooling circuit repairs
• Laboratory: Gas distribution line extensions, instrument air circuit repairs

Package Contents

23, 60, 80, or 100 pieces (select above) — PU4, PU6, PU8, PU14 straight push-to-connect union fittings in assorted quantities, supplied in organized storage box.