I note that there are a few sellers that offer for auction small plastic discs that supposedly help you to make a balloon arch.  I don't mean to dispute them as they are probably inexperienced as no balloon professional to my knowledge uses these items to create balloon arches.  There are easier methods to create balloon arches and most balloon decorators will explain that to you in the products they sell.  IN my humble opinion, these balloon discs, make the creation of an balloon arch more difficult than simple duplet and cluster creation.  I am only trying to prevent you from wasting money on these foolish items.  They will NOT SAVE YOU TIME.  ASK A SOMEONE WHO HAS BEEN IN THIS BUSINESS FOR SOME TIME.  There are several on  EBAY who are reputable.