Metric L and S Series Fitting Chart

What it is

Metric 24° cone fittings (ISO 8434-1, formerly DIN 2353) join metric tube with a cutting ring or an O-ring cone (often called DKO). They come in series:

• L (light) series: for lower pressures; thinner nuts.
• S (heavy) series: for higher pressures; heavier nuts and bodies.
• LL (extra light) series also exists for small tube.

Fittings are named by series and tube OD in mm, for example 12L or 16S.

How to identify

• Measure the tube OD in millimeters.
• Measure the thread OD and pitch. These threads are metric fine, usually 1.5 mm or 2 mm pitch.
• Check the cone. A 24° cone accepts a cutting ring or an O-ring cone end.
• Use both the tube OD and the thread to choose the series. Thread size alone can mislead.

L and S series chart

Key points

• Several L and S sizes share a thread. For example, 8L and 6S both use M14x1.5; 12L and 10S both use M18x1.5; 15L and 14S both use M22x1.5. The nuts will thread on, but the tube and cone sizes are different.
• Always give series and tube OD when ordering, not just the thread.
• Cutting rings must be pre-set and assembled per the maker's method. The ring bites the tube once and should not be moved to a new tube.
• Stud ends into ports may be metric (ISO 6149 or ISO 9974) or BSPP. Check the port thread separately.

Common mistakes

• Ordering by thread size and getting the wrong series.
• Reusing a cutting ring on a new section of tube.
• Mixing cutting ring parts from different makers.

Governing standards: ISO 8434-1 (24° cone connectors); ISO 6149 and ISO 9974 (metric ports); fitting manufacturer assembly data.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.