Pen injectors for the administration of insulin have been available since the 1980s. The first insulin pen, NovoPen®, was introduced by Novo in 1985 (http://http://www.novonordisk.com/about_us/history/step-by-step.asp). In the years since, insulin pens have seen innovation in both features and functionality, and many more manufacturers have entered the market. This analysis discusses several features and design alternatives of insulin pens and comments on a new study by Bohnet and coauthors in this issue of Journal of Diabetes Science and Technology that compared the dosing accuracy of the spring-driven FlexTouch® (FT; Novo Nordisk; insulin aspart) with that of the manually operated SoloSTAR® (Sanofi; insulin glulisine). The volumetric flow rate of insulin delivery with FT was also evaluated.