Costco will do 135 for $1.60 per 36 exposure roll, but they do not do 20. I used Unicolor 1 liter from FreeStyle for 135, 120 and 4"x5". It says it will do 8 rolls of 135-36 but I have easily gotten 12 rolls from it. I do not know how many rolls the other sets from FreeStyle handle.