PMU Needle Cartridge Codes Explained: What Do the Numbers and Letters Mean?
"1RL," "5F," "3RS" — cartridge codes look cryptic until you know the pattern. Once you do, you can read any cartridge label and know exactly what it's built to do.
Elite Permanent Makeup & Cosmetology College has trained licensed PMU artists in Los Angeles since 2012 and is licensed by the California Bureau for Private Postsecondary Education (BPPE). Last reviewed: August 2026.
Quick answer: The number is the needle count, and the letters describe the arrangement: RL (round liner), RS (round shader), F (flat shader). So "5F" means 5 needles in a flat shader arrangement, and "3RL" means 3 needles in a round liner arrangement. A separate diameter spec (like 0.30mm) describes how fine or bold each needle is.
Breaking down the code
| Part of the code | What it means |
|---|---|
| Number (1, 3, 5, 7, 9...) | How many needles are grouped in the cartridge |
| RL | Round liner — tightly packed, round grouping, for lines |
| RS | Round shader — loosely spaced, round grouping, for soft fill |
| F | Flat shader — flat row arrangement, for broad even shading |
Putting it together with real examples
- 1RL — 1 needle, round liner arrangement. Fine lines, hair strokes.
- 3RL — 3 needles, round liner arrangement. Bolder lines.
- 3RS — 3 needles, round shader arrangement. Soft fill, eyeliner and lip shading.
- 5F — 5 needles, flat shader arrangement. Powder brow shading.
- 9RL — 9 needles, round liner arrangement. Bold, dense lines or larger-area outlining.
Diameter: the code doesn't cover it
The RL/RS/F code tells you needle count and arrangement, but not the individual needle diameter — that's usually listed separately, often in the 0.18–0.35mm range. Two cartridges with the same code (say, two different 5F products) can still produce different results if their diameters differ, so check both specs together rather than relying on the code alone. For how diameter affects a specific technique, see 5F vs. 7F for Powder Brows.
Frequently asked questions
Does a higher number always mean a bolder result?
Generally within the same letter category (more RL needles means a bolder line), but comparing across categories — like a 5RL to a 5F — the letter matters as much as the number, since they're built for different jobs.
What does "M1" or similar codes on some cartridges mean?
Different manufacturers sometimes use additional codes for specialty configurations beyond the standard RL/RS/F system — always check the specific product's description rather than assuming a universal standard across every brand.
Why do two cartridges with the same code feel different?
Needle diameter, taper, and material quality can all vary between manufacturers even when the RL/RS/F code and needle count match, so results can differ even with an identical code.
Where can I see the full range of configurations available?
See the complete Needles & Cartridges collection for the full range of codes and diameters stocked.
This article is educational information for licensed PMU professionals.