Guide · Measuring and buying
Joining metric 4/7 mm and 16 mm tubing to US drip parts
Will 4/7 mm drip tubing fit 1/4 inch parts, or 16 mm fit 1/2 inch? Only if the listing states the actual ID and OD. What to compare, and what is not confirmed.
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Short answer
Metric names are not US sizes. "4/7 mm" usually means 4 mm ID x 7 mm OD, but sellers differ, so get the listing's actual ID and OD and compare them with the US part's stated size. If either number is missing, no fit can be confirmed, and that goes for 16 and 17 mm tubing too.
What the metric names mean
Imported drip kits label tubing by millimeters, often as a pair such as 4/7 mm or 13/16 mm. The usual reading is inside diameter, then outside diameter, but a single number like "16 mm" can mean either. Treat the label as a starting point and look for both numbers on the listing.
Even sellers say so. AquaGrow's 4/7 mm barbed tee asks buyers to confirm the actual inner and outer tubing dimensions before ordering, and lists no pressure rating.[1]
4/6 and 4/7 mm vs US 1/4 in
Some makers put metric and inch names on the same family. Claber groups its tubing into a 4-6 mm family it labels 1/4 in and a 13-16 mm family it labels 1/2 in.[2] Its 90371 feeding tube is a 5 m polyethylene tube labeled 1/4 in, 4-6 mm.[3]
US 1/4 in tubing is itself several sizes. DIG's 2016 catalog lists 1/4 in polyethylene micro tubing at .170 x .250 in.[4] DIG's vinyl table lists .156 x .245, .160 x .220 and .170 x .250 in.[5]
For comparison only (1 in = 25.4 mm): 0.170 in is about 4.3 mm and 0.250 in is about 6.4 mm. That arithmetic tells you how close two numbers are. It is not a fit statement, because no maker here lists a metric tube for a US barb or the reverse.
Antelco describes its SPEC Drip emitter as having a barbed outlet for 4 mm ID tubing.[6] It was announced on Antelco's EU site, and we have not established US or Canada availability.
16 and 17 mm vs US 1/2 in
On the US side, makers also use millimeters:
- DIG labels its 1/2 in barbed fittings as 16 and 17 mm.[7]
- Rain Bird describes its XF dripline insert fittings as 17 mm barb-style fittings rated 0 to 50 psi.[8]
- Netafim lists Techline CV at 0.66 in OD, 0.56 in ID and 0.050 in wall, in inches only; it does not call the tubing 17 mm.[9] Its page links a 17 mm fittings section and a dealer locator but names no approved fittings.[9]
- A distributor listing for Irritec's 600 Series hose coupling gives an acceptable tubing ID of .590 to .630 in and a wall of .025 to .050 in.[10] Its printed millimeter wall range does not match those inch values, so quote only the inches.[10]
- Rain Bird's Easy-Fit page lists its compression fittings for 0.63 to 0.70 in OD and also mentions 16 to 18 mm OD tubing.[11]
So "16 mm" or "17 mm" alone does not tell you whether a barb or a compression fitting will hold. You need the ID for a barb and the OD for a compression fitting, in the listing's own numbers.
Threads on imported kits
Faucet and filter threads on imported kits may not be US hose or pipe thread. Check every threaded joint with the thread guide before you mix parts. Do not adapt imported electric timers; powered parts are outside what we cover.
What to check before you mix parts
| Metric name on the listing | What the listing must state | US part to compare |
|---|---|---|
| 4/7 mm or 4/6 mm | Actual ID and OD in mm or inches | 1/4 in tubing at its stated ID x OD, such as .170 x .250 in |
| 4 mm outlet barb | The tubing ID the barb is made for | Your 1/4 in tubing's ID |
| 16 mm or 17 mm tubing | ID and OD, not one number | 1/2 in tubing and fittings at their stated OD or ID range |
| 16 or 17 mm fitting | Barb (ID) or compression (OD), and the range | Your tubing's measured ID or OD |
If the listing cannot give you both numbers, treat the part as unconfirmed and keep the systems separate.
A US part with a stated metric range
If you have measured tubing from an imported kit and its OD falls inside a US maker's stated range, you can use that maker's fitting by its own numbers. Rain Bird's Easy-Fit coupling is listed for 0.63 to 0.70 in OD, and the page also mentions 16 to 18 mm OD tubing.[11] For 1/4 in, Rain Bird lists XQ tubing at 0.17 x 0.25 in,[12] which gives you a known US size to run from a metric kit's manifold only if that manifold's barb is stated for a .17 in ID.
Picks that fit3 products
Rain Bird EFC25-1PS: one Easy-Fit coupling, only for tubing you have measured at 0.63-0.70 in OD.
More on choosing
Rain Bird XQ100 or Raindrip 016010T: 100 ft of 0.17 x 0.25 in tubing, only where the barb is stated for that ID. On Amazon, check that 'Ships from / Sold by' shows Amazon.com or the brand.
Choose the Rain Bird Easy-Fit EFC25-1PS for 0.63-0.70 in tubing
Rain Bird Easy-Fit EFC25‑1PS 1/2 in universal compression coupling (0.63‑0.70 in OD)
1/4 in polyethylene tubing with ID and OD stated
1/4 in polyethylene tubing, 100 ft, ID and OD stated
Raindrip 016010T 1/4 in black polyethylene supply tubing (0.170 x 0.250 in, 100 ft)
Next
Questions
Will 4/7 mm tubing fit 1/4 inch fittings?
Not confirmed by name. Get the listing's actual ID and OD and compare them with the US part's stated size; AquaGrow itself asks buyers to confirm the dimensions of its 4/7 mm parts.[1]
Is 16 mm drip tubing the same as 1/2 inch?
Not necessarily. DIG labels its 1/2 in barbed fittings 16 and 17 mm, and Rain Bird's Easy-Fit page mentions 16 to 18 mm OD tubing, but a single '16 mm' can mean ID or OD. Compare the stated numbers.[7][11]
What does 4/7 mm mean?
Usually 4 mm inside diameter and 7 mm outside diameter, but sellers differ, so check the listing's stated dimensions.
Can I connect an AliExpress drip kit to Rain Bird parts?
Only where the kit's listing states an ID or OD inside the Rain Bird part's stated range, such as Easy-Fit's 0.63-0.70 in OD. If the listing gives no dimensions, no fit can be confirmed.[11]