Adafruit PCB Ruler - 1554
The first time you soldered up a surface mount component you may have been surprised "these are really small parts!" and there's dozens of different names too! QFN, TDFN, SOIC, SOP, J-Lead, what do they mean and how can you tell how big they are? Now you can have a reference board at your fingertips, with this snazzy PCB reference ruler.
Measuring approx 1" x 6", this standard-thickness FR4, gold plate ruler has the most common component packages you'll encounter. It also has font size guide, trace-width diagram, and a set of AWG-sized drills so you can gauge your wire thicknesses. Edges are labeled in inches with 1/8th marks and cm with 0.1cm marks.