# How to read a Beru spark plug reference

> A Beru technical code encodes the thread & seat, resistor, heat rating, reach, electrode and material. Here is how to decode it.

A Beru technical code such as **14 FR-6 LDU3** is read left to right: the **thread size**, the **seat / configuration** letters, the **heat rating** after the dash, then **reach, electrode and material**. (Beru also prints a short catalogue code like **Z194**.)

## 1. First number — thread

NumberThread
10M10×1.012M12×1.25
14M14×1.2518M18×1.5

## 2. Letters — seat & configuration

- **F** / **S** / **V** — flat seat (with gasket)
- **K** — conical (taper) seat; **T** — small-engine taper seat
- **G** — surface-gap plug; **GH** — surface gap with auxiliary spark path
- **R** — built-in interference-suppression resistor (5 k/10 k)
- **Z** — two-stroke-engine plug; **ZR** — Bi-hex (double hexagon)

## 3. The number after the dash — heat rating

Beru's **heat rating** (Wärmewertkennzahl) runs on a new scale (e.g. 6, 7, 8…): a **lower number is colder**, a higher number hotter. It maps to an older 25–400 scale. It is relative to Beru.

## 4. Reach & spark position

A letter (A, B, C, D…) codes the **thread length / spark position** — e.g. A/B ≈ 12.7 mm reach, C/D ≈ 19 mm reach.

## 5. Electrode & material

- Ground electrode: **T** triangular, multipolar variants
- Material: **U** Beru ultra (NiCu), **S** silver, **P** platinum, **I** iridium, **E** nickel-AL

## 6. Tightening torque

Torque depends on the seat, thread diameter and cylinder-head material. Flat seat (with gasket): 10 mm 10–15 N·m (iron) / 10–12 (alu), 12 mm 15–25 / 15–20, 14 mm 25–35 / 25–30, 18 mm 35–45 / 35–40. Taper seat: 12–14 mm 10–20 N·m, 18 mm 20–30. Always follow the value printed on the box.

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*Source : [How to read a Beru spark plug reference](https://www.thesparktwin.com/en/guide/nomenclature-beru/) — TheSparkTwin*