Staedtler Marsmatic Technical Pens Maximum precision with a steady inkflow due to Staedtler's ink collector system Hard chrome-plated drafting nibs with no drying up of ink with double sealing system in the pen cap Suitable for use on tracing paper ans matt drafting film Easy to refill from bottle or with cartridges. Ink not including Available in 0.18, 0.25, 0.35 and 0.50 with corresponding replacement nibs Technical advice on how to use your Staedtler Pens Never disassemble the point portion of your technical pen, since the tiny filament wire can be easily damaged. When ink dries, it undergoes a transformation in its chemical composition and cannot be "reconstituted" with water. It is extremely important to clean your pens if they aren't going to be used for more than a day or two. Otherwise, the filament wire can get stuck in the dried ink and break off! If this happens, the point is ruined, since the filament wire cannot be replaced. The best way to clean a technical pen that has dried out is with an ultrasonic cleaning machine, which actually vibrates the particles loose. In the attached document you can see how to clean pen points if you do not have an ultrasonic cleaning machine. Furthermore it is important that you always use the proper ink. Fountain pen inks are not suited for technical pens. The points are generally made of stainless steel, tungsten carbide, brass and plastic. Non-technical pen inks contain chemicals that may be corrosive to these materials. Please be aware that drawing inks have a limited shelf life. If the ink looks grey or has floating particles, it has deteriorated and should be discarded. If the pigments in the ink have "fallen out of suspension"; shaking will only lead to clogging caused by larger pigments. Mixing inks or adding water or thinners will also deteriorate the ink.