Sacs sizes are given as the diameter measured in n/64ths of an inch. Sizing a pen involves measurement of the sac nipple on the section in n/64ths of an inch. This is a starting point, judge sac size based on how it slides in the barrel.
Fifteen Pens is currently closed for vacation. Any orders placed during this time will be processed and fulfilled the week of December 7th. Thank you for your patiences and understanding.