I tried these out in several Pentel models (GraphGear 500, for example) and they fit perfectly, without slop in the lead shield, and feed easily. Package says made in Japan, packaged in France, so we might presume they are made by one of the major Japanese makers of mechanical pencil leads: Uni, Pentel, etc.These are not excessively fragile, although they are not as strong as standard 0.9mm graphite leads. Absolutely no issues with breaking, snapping or crumbling when advanced the usual two clicks out of a mechanical pencil. Stronger than 0.3mm graphite leads, perhaps slightly more fragile than 0.5mm graphite leads.I tested these on black knit T-shirt fabric, green file folder heavy paper, and 1000D and 200D nylon cloth. They made legible marks on all four materials, although the heavy texture of the 1000D Cordura was hard for the lead to deal with. While clean and consistent, I would not call the marks opaque or dense. Casual contact slightly lightened, but did not rub out, the marks, while they easily erased with a white vinyl draftsperson's eraser. These are not like the typical red and blue leads for mechanical pencils. Instead of being waxy and hard to erase with unimpressive pigment load, these really are chalky without obnoxious amounts of binder.These are "a bit" expensive, even by the standards of someone who seeks out premium writing tools and materials, which is why I did not give a top rating for "Value for Money". If you want a dense mark on dark fabric, you are better off using conventional tailor's crayons or tailor's chalk. But then you have all the issues (and mess) of resharpening and of trying to navigate a hunk of wax or chalk along a pattern. These white leads will always draw a consistent line width, never need resharpening, and will reach into the corners of the most intricate sewing pattern.

👍👍👍

I've tried many different marking pencils for quilting and this is the sharpest and sturdiest pencil I have ever used. The refill leads are not cheap, but they are well worth it in my opinion!

They fit my Prym chalk pencil, and are of similarly good quality as the Prym chalk refills (which I couldn't find on here at the time of ordering)

This is one of my favourite tools for handlettered signs. It's easily erasable and makes really thin lines.