Alvin Tech-Liner Technical Pen Marker - Contain extremely fine polyacetal plastic nibs set in 0.5mm stainless steel sleeve for protection. These superpoint pens are ideal for precision drafting. Free-flowing ink and slim design offer a perfect balance for free-hand drawing or for any design work. These disposable technical pens are offered in five line widths and contain a permanent, waterproof ink that dries instantly. Note: Sets are supplied in protective vinyl sheath.