The other day I bought some kirby bags for the g6 and ultimate G and I have a g5....I installed the g6 and ultimate G bag into my G5 and I was wondering if its ok to use G6 and ultimate G bags on my G5?......

If it fits on the adaptor, it's fine to use the new bags. Additionally, Kirby's replacement outer bags for the older (G3 and earlier) machiens are available in the Micron Magic material. Here in St. Louis, Rick Asquith recommends -insists, really- that Kirby outer bags be so replaced and their filtration thus improved.