There are two 'tips' available - standard and micro. The microtip allows for finer control but is a little harder to use (because it doesn't deposit as much silver at once).The CW2200STP (standard tip pen) has an orifice size of 1 mm and will draw traces that will average 2.0 mm in width. The CW2200MTP (micro-tip pen) has an orifice size of 0.7 mm and will draw traces that average 1.5 mm in width. See the image above with a demonstration of the kind of traces you can draw with each of the lines (by someone with no practice :)
Adafruit strongly suggest reading the excellent tutorial document written by the makers which discusses use, shelf life, safety, soldering, and more!