Bock vs Jowo: Why the Difference Matters
Bock (C. Josef Lamy spinoff, now independent) and Jowo (Joh. Wolfram & Sohn) are the two dominant German manufacturers of fountain pen nib units. Both produce #6 format nibs to broadly similar specifications — but their housing geometries are not interchangeable, and choosing the wrong nib for your pen section will result in ink leaks, hard starts, or poor fit.
Bock #6 Type 250 Series: Geometry & Characteristics
The Bock Type 250 is a screw-in nib unit designed for Bock's proprietary housing collar system. Key specifications:
- Shank diameter: 6.0mm with a pronounced tail curve that locks into the Bock collar housing
- Collar thread pitch: M6 × 0.5 (fine thread)
- Feed geometry: Bock-profile capillary channel tuned for Bock's feed dimensions
- Dual-view inspection: The Bock unit allows front-face and reverse feed channel inspection due to its screw-in design
Jowo #6 Type 250 Series: Geometry & Characteristics
Jowo #6 nibs use a press-fit or threaded collar design common to most modern bespoke pen sections. Key specifications:
- Shank diameter: 6.0mm with standard German shoulder curvature
- Section compatibility: Fits Jowo threaded units and most modern acrylic/ebonite pen sections from artisan makers
- Universal fit: The Jowo #6 is the de facto standard for custom pen makers in India and globally
Which Should You Choose?
The decision is almost entirely determined by your pen section, not personal preference:
- If your pen uses a Bock Type 250 housing unit, you need a Bock #6 compatible nib. The Bock tail curve will not fit a Jowo housing correctly.
- If your pen uses a standard threaded section from an artisan maker, pen kit supplier, or modern bespoke atelier, you need a Jowo #6 compatible nib.
- If you are building a pen from scratch with an RS ebonite section, our Jowo-compatible nibs are the recommended choice as they pair with our Jowo-profile ebonite feeds.
Available Finishes from RS Writing Instruments
Both Bock and Jowo compatible nibs are available in three finishes:
- Stealth Black PVD: High-durability physical vapour deposition matte black. Scratch-resistant and consistent in appearance.
- Premium Golden: Gold-tone PVD for classic elegance. Pairs well with gold-trimmed pen sections.
- Rose Gold: Warm rose gold tone. Increasingly popular for bespoke collector pens.
Point Sizes: EEF to Double Broad
All RS nib units are available in six German-standard point widths:
- EEF (Extra Extra Fine): ~0.3mm line width. For extremely fine detail work and Japanese-style character writing.
- EF (Extra Fine): ~0.4mm. Precise everyday writing without being scratchy.
- F (Fine): ~0.5mm. The most popular size globally.
- M (Medium): ~0.6mm. Balanced expressiveness and legibility.
- B (Broad): ~0.8mm. Shading and wet writing. Excellent with shimmer inks.
- BB (Double Broad): ~1.1mm. Maximum expressiveness. Calligraphy and signature pens.