Fibre and plastic tipped drawing pens have come to dominate the world of drawing pens. Certainly for freehand sketching and drawing they're a whole lot easier to manage than traditional steel-nib drawing pens. Mostly disposable, and generally good value, these are all excellent pens with high quality lighfast and waterproof drawing ink. Most have a large range of sizes, and some have a range of ink colours. The downside? Line sizes. When a steel technical pen says 0.5mm that's the line width it makes and will always make. Fibre pens don't really have consistent line widths - the quoted 'size' on the pen has no bearing on the line width. An '05' pen does not create a 0.5mm line, ven if they cheekily add 'mm' after the 05 or put a decimal point in between 0 and 5. Being fibre, they also start to wear and will inevtiably begin to create thicker and thicker lines as they soften over time. For many purposes this isn't going to matter, but if accuracy and ISO standard line widths is your thing, you should really be looking at steel drawing pens.