The first time you soldered up a surface mount component you may have been surprised "these are really small parts!" and there's a dozen 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" standard-thickness FR4, this gold plated ruler has the most common component packages you'll encounter. It also has font size guide, trace-width diagram, and a set of schematic symbol guides so you can keep track of your transistor pinouts.