Aquarium airline tubing and fittings: 3/16 in vs 4 × 6 mm, check valves, connectors and Luer barb match — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/aquarium-airline-tubing/  (sheet CC BY 4.0)
Basis: retailer and maker listings read (Bluviva, Perfect Ponds & Koi, Lee's, Aquaneat, Penn Plax); only the tubing ID and OD are printed, no fitting dimensions
Catalog version: 2026-10-20

Sizes: see table below
- Two sizes are sold as standard airline tubing: 4 mm ID × 6 mm OD (metric listings) and "3/16 in" (US listings). The 4 mm and 3/16 in (4.76 mm) are not the same number, and the US listings read here do not print the OD of their 3/16 in tube, so the page does not claim the two are interchangeable; the 3/16 in value is the tube's nominal size, and Lee's calls it the ID of the tube its check valve takes.
- Fittings (check valves, 2- and 3-way valves, L- and T-connectors, splitters) are listed as 'for 3/16 in' or 'for 4 mm' tubing. No listing read prints a barb diameter, length or port size for these parts, so there are no fitting dimensions here and no files.
- A Luer barb that fits this tube: the nearest sizes in Nordson's and Qosina's tables are 5/32 in (4.0 mm ID) and 3/16 in (4.8 mm ID) tube barbs, see luer-to-barb-adapters. Silicone and PU push-fit tube sizes (including the 4 × 6 mm tube) are on silicone-tube-and-fittings.
- Not covered: pump outlet nozzle diameters, air-stone barbs and CO2 tubing, which were not read.

item  ID  OD  wall  source
airline tubing, metric  4 mm  6 mm  about 1 mm (computed, (OD − ID)/2)  Bluviva ("4/6 mm" as the usual size for most air pumps and attachments); Perfect Ponds & Koi (4 mm ID, 6 mm OD)
airline tubing, "3/16 in"  3/16 in (4.76 mm, computed)  not printed  not printed  Aquaneat listing: "Standard 3/16 in" tubing; Penn Plax listing: "3/16 in" (no ID/OD split in either); Lee's: pumps that use 3/16 in ID tubing
L-shaped connector  for 4 mm ID tubing  —  —  Aquaneat listing (no part dimensions printed)
air control valve (2-way / 3-way)  for 4 mm tubing, or "3/16 in ID"  —  —  Aquaneat listings (no part dimensions printed)
check valve  for 3/16 in airline tubing  —  —  Lee's 12405, Aquaneat and other listings read (no part dimensions printed)

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Bluviva: Airline and fittings category: standard airline tubing 4/6 mm (ID/OD); fittings should match the tubing — web — Retailer page; numbers only — https://bluviva.com/product-category/equipment/aeration/airline-fittings/
- Perfect Ponds & Koi: H/D clear per meter airline 4 mm ID, 6 mm OD — web — Retailer page; numbers only — https://www.perfectpondsandkoi.co.uk/products/per-meter-airline-h-d-clear-4mmid-6mm-od
- That Pet Place (Lee's check valve 12405): Lee's airline check valve: all air pumps that use 3/16 in ID tubing — web — Retailer page; numbers only — https://www.thatpetplace.com/check-valve-1pk_2
- Walmart listing (Aquaneat airline tubing): Standard 3/16 in airline tubing; check valves for 3/16 in tubing; L-shaped connectors and air control valves for 4 mm ID tubing — web — Retailer listing; numbers only — https://www.walmart.com/ip/Aquaneat-Aquarium-Airline-Tubing-40Feet-Standard-3-16-Tubing-for-Air-Pump/541130335

No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.
API: https://xemstudio.com/api/geometry?object=aquarium-airline-tubing