If you own a Kirby and trying to buy bags on eBay, you are probably confused or paying more and buying the identical bag you are using for your Kirby. I will explain you very briefly how buying a Kirby bag works here. I only do this for living for the last 15 years :) So bear with me...
Kirby got bags for older models and G3, G4, G5, G6, Diamond, Sentria. These bags come in different filtrations. The ultimate filtration bag for Kirby is the cloth bags. They are white and they are not paper !!! If you have any allergies, asthma or etc buy the white cloth Kirby bags and you are worry free. White bags with blue plastic bag (original Kirby) fits all G series !!! Sentria has F series whit ebags that twists and snaps. So there is one kind of white cloth bag for all G series and 2 kinds whit ecloth bag for Sentria.
If you are going to buy HEPA filtering macron magic bags for your Kirby, you do not need to buy the ecxpensive one. Here is how it works. Let's say you got a G6 Kirby vacuum cleaner. You can use white cloth bags (most expensive), you can use G6 bags (a little less expensive) or you can use g4/G5/G3 bags (much cheaper) and they will all work fine wth your G6 cleaner. The bottom line is if you got a cleaner that is newer than what bags say on it, it fits. You can use G3 bags on your G4 G5 G6 vacuum cleaners. You save at least 30-40% depending on where you buy them from.
One more quick tip. The belt for your Kirby is a $1 or free with purchase of bags at auctions. Please change your belt every 6 months regardless of it is broken or not. Belt streches out and your roller starts skipping resulting poor performance. All because of a $1 belt. Belts need to be changed every 6 months you use your vacuum or not ! It stretches and your vacuum stops picking up right.
Remember the rule: If your green light on the power head flickers it is way past the time for changing your belt. If you are not seeing your green lght when you turn on your Kirby, your roller is not turning !!!
I hope information helps.
Happy and safe cleaning !!!