I believe it's this pen! I tend to re-name the pens that I use, but I always keep the downloaded source in case I need to find it again for someone!
As for pen size, it's actually 52.6 px. However, I do work with a larger canvas most of the time (2000 X 15000), so the size is kinda there to match that. I'd say fool around until you find your best pen size. What's nice about this pen is that the quality is more or less the same, depending on how big of a canvas you work with!