One thing I've never seen is a chart comparing the different pen sizes. I don't know just how helpful this is, since tiny differences in pen girth = huge differences in the feel of the pen.
- 1-Pocket Pen
- 2-Slimline (modified)
- 3-Sierra
- 4-Pentel Conversion
- 5-European
- 6-Tall Slimline
- 7-Jr Gentleman's
- 8-Jr Majestic
- 9-El Grande
I hope this helps!