--- title: "Pneumatic Tubing 6/4 and 8/6 mm: Dimensions and Selection" canonical: "https://yuannaitube.com/pneumatic-tubing-6-4-and-8-6-mm/" language: "en-US" --- RESOURCES # Pneumatic Tubing 6/4 and 8/6 mm: Dimensions and Selection By [YUANNAI TUBE]() Published 2026-10-28Updated 2026-11-03 ![Four short pneumatic tubes in blue, black, orange and clear cut at an angle to show the wall, beside two push-in fittings]() ## Pneumatic tubing 6/4 and 8/6: the short answer In German pneumatics a tube is named by outside and inside diameter: 6/4 means 6 mm OD and 4 mm ID, so a wall of 1.0 mm; 8/6 means 8 mm OD and 6 mm ID, also a wall of 1.0 mm. The OD is the size that has to match the fitting. At the same OD, the thicker wall of an 8/5 tube (1.5 mm) carries more pressure than an 8/6 tube. ## How 6/4 and 8/6 are written Our model numbers write the same sizes as four digits: 0640 is 6 mm OD and 4 mm ID, 0860 is 8 mm OD and 6 mm ID. The **wall thickness** is (OD minus ID) divided by 2. Use the [unit converter]() to calculate it for any size. ## Working pressure and bend radius at 6/4, 8/6 and 8/5 The table lists the **working pressure** in bar at 23 °C and the minimum **bend radius** in mm from our model tables. The **PU tubing** table is shown with its **bend radius** only; read the **working pressure** of **PU tubing** on the [PU tubing page]() . | Size (OD/ID) | Material | Model | Working pressure (bar) | Min. bend radius (mm) | | --- | --- | --- | --- | --- | | 6/4 | PU | YN-PU 0640 | see product page | 15 | | 6/4 | Polyether | YN-PUR 0640 | 10 | 25 | | 6/4 | PA6 | YN-PA6 0640 | 35 | 35 | | 6/4 | PA12 | YN-PA12 0640 | 27 | 30 | | 6/4 | Composite V8 (PU outer layer) | YN-0640 V8 | 14 | 15 | | 6/4 | Composite V9 (polyether TPU outer layer) | YN-0640 V9 | 14 | 16 | | 8/6 | PU | YN-PU 0860 | see product page | 25 | | 8/6 | Polyether | YN-PUR 0860 | 8 | 40 | | 8/6 | PA6 | YN-PA6 0860 | 23 | 48 | | 8/6 | PA12 | YN-PA12 0860 | 17 | 50 | | 8/6 | Composite V8 (PU outer layer) | YN-0860 V8 | 12 | 20 | | 8/6 | Composite V9 (polyether TPU outer layer) | YN-0860 V9 | 12 | 29 | | 8/5 | PU | YN-PU 0850 | see product page | 20 | | 8/5 | Polyether | YN-PUR 0850 | 12 | 30 | | 8/5 | PA6 | YN-PA6 0850 | 28 | 45 | | 8/5 | PA12 | YN-PA12 0850 | 29 | 30 | | 8/5 | Composite V8 (PU outer layer) | YN-0850 V8 | 15 | 20 | | 8/5 | Composite V9 (polyether TPU outer layer) | YN-0850 V9 | 15 | 29 | Three patterns stand out. PA6 carries the highest **working pressure** at 6/4 and 8/6. At 8/5, PA12 matches PA6, and every material carries more than at 8/6, because the wall is 1.5 mm instead of 1.0 mm. And PU, polyether and composite tubes bend at a smaller radius than PA6 at the same size. ## Which material for 6/4 or 8/6 - **PU and polyether:** flexible, tight **bend radius**, for moving connections and short runs. See [polyether tubing]() . - **PA6:** the highest **working pressure** of the four, firmer, larger **bend radius**. See [PA6 nylon tubing]() . - **PA12:** usually more flexible than PA6 (a smaller **bend radius** at 6/4 and 8/5, about the same at 8/6), for routing where pressure also matters. See [PA12 tubing]() and the [PA6 vs PA12 comparison]() . - **Composite:** a PU or polyether TPU outer layer over a PA12 inner layer. See [composite tubing]() . For PU or nylon, the [PU vs nylon selection checklist]() walks through flexibility, pressure, temperature and fitting hold. ## Matching the fitting - A 6 mm push-in fitting takes a 6 mm OD tube; an 8 mm fitting takes an 8 mm tube. The ID does not set the fitting size. - A 6 mm tube is not a 1/4 in tube. The two differ by 0.35 mm, more than the tolerance of ±0.10 mm on our **nylon tubing**. Do not mix metric tubes with inch fittings. - The wall matters too: at 8 mm OD, 8/5, 8/5.5 and 8/6 tubes have the same OD but different pressure ratings. See [matching tubing to fittings]() . ## Frequently asked questions What does 6/4 mean on a pneumatic tube? It is the outside and the inside diameter in mm: 6 mm OD and 4 mm ID, which gives a wall of 1.0 mm. Is 8/6 or 8/5 better for higher pressure? 8/5. At the same 8 mm OD, the 1.5 mm wall of an 8/5 tube carries more pressure than the 1.0 mm wall of an 8/6 tube. For PA12 the working pressures in our tables are 29 bar at 8/5 and 17 bar at 8/6. Which tube fits a 6 mm push-in fitting? A tube with a 6 mm outside diameter, for example 6/4. Check the fitting maker’s data for the wall range it accepts. Can I use PU tubing at 6/4 in place of nylon? Only if the **working pressure** and temperature of your circuit are within the PU rating. Nylon carries more pressure at 6/4, while PU bends at a smaller radius. Compare both on the data sheets. ## Request a sample [request a 1 to 3 m sample]() at your size, or [see the full size chart]() for sizes beyond 6/4 and 8/6: [send your requirements]() . ## Sources and scope - [PU Tubing — English data sheet (v3-20261020)]() - [PA6 Nylon Tubing — English data sheet (v4-20261020)]() - [PA12 Nylon Tubing — English data sheet (v5-20261020)]() Use these documents for the identified product models and stated test conditions. General material comparisons and selection checklists do not establish a different grade’s rating, fitting compatibility or project approval. Confirm the exact model, medium, temperature, pressure and required evidence before ordering. Content review: [zhangkexin]() · Marketing Review scope: market information and document references. ## Tell us what your application needs. Send your dimensions, operating conditions and quantity. Let’s identify the right tubing for your project. [Request a Quote →]() ## Related tubing products ![PA12 Nylon Tubing]() [PA12]() ### PA12 Nylon Tubing PA12 nylon tubing for pneumatic, hydraulic-oil and fuel lines. 14 models from 2.5 x 4 mm to 12 x 16 mm and 1/8″ to 1/2″, in 100 m or 200 m rolls. [View details →]() ![PA6 Nylon Tubing]() [PA6]() ### PA6 Nylon Tubing PA6 nylon tubing for fixed pneumatic, oil and fuel lines. 14 models from 2.5 x 4 mm to 12 x 16 mm and 1/8″ to 1/2″, in 100 m or 200 m rolls. [View details →]() ![PU Tubing]() [PU]() ### PU Tubing PU tubing for compressed-air, inert-gas and vacuum lines. 15 models from 2.5 x 4 mm to 12 x 16 mm and 1/8″ to 3/4″, in 100 m or 200 m rolls. 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