I mainly use 1/4" diameter dowels and cut each 3 ft long dowel in half, giving me 2 - 18" dowels from each. My oven is just over 18" wide inside, so that size works quite well for me. I've only done 3/8" wide ribbon and 1/4" once, but I've been thinking of doing some teeny ones. Just don't know if I'll need to get narrower dowels for that. Does anyone else make the teensy korkers out of 1/8" ribbon?
From each 18" piece of korker ribbon, I usually get 6 - 3" korkers + a little extra that I put in my korker scrap bag to use on clippies or as bow accents.