Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: Which bag does it use
Document: this thing is easy to use, light, powerful and we have a 4000 square foot house. We fill up the bag in just three or four uses, not even vacuuming every room. It is a big pain in the butt for this reason as those bags are expensive. But I cannot complain about the quality of the vacuum. Tiny bags if you've got a big house with more than four kids in it.
The vacuum picks up nearly everything and it's easy to use. There's no weird smell when I turn it on (from the bag) as was the case with my old vacuum cleaner. I like that I can turn the power off on the handle without changing any attachments when going from hard floor to carpet. The cannister rolls smoothly and hasn't given me any issues. The bags are rather expensive, so I hope they're large and last a long time.
If you like canister vacs, this is a pretty good one. I was talked into getting this because of the high quality of the Miele brand. It is light weight and easy to use. It has a long extension so it is easy to reach tops or curtains and ceiling corners, and it has several attachments for crevices, curtains, and furniture.However, like with any canister, it has a bag and will lose suction as the bag fills.Next time, I'm getting a bag less vac.
It is also about half as loud as my Electrolux which everyone will appreciate. It does have a manual bag full indicator which is nice. We spent another $100 to get that on the Electrolux but it never did work, was never happy about that! I bought less expensive mags from 3M instead of the Miele brand. 3M makes good products so I am confident it will be ok as 3rd party products usually have to meet obvious product requirements. I would not use cheap paper bags.
Less cumbersome and lighter weight also means less fatigue for this chore, making at least this aspect of housecleaning much more pleasant. Our house is one story, with a combination of laminate, tile, permanent (old crappy) carpeting, and throw/area rugs. The adjustable suction settings are indispensable for thorough cleaning, without damaging upholstered furniture or delicate rugs.Another big difference between the two canister models is the use of a disposable collection bag for the Miele.
It has to be unplugged in order to get access to the dust bag..4. Other than the power brush, there are no other accessories that are included in the purchase..5. The power cord is short.
Overall, I have NO REGRETS with purchasing the Miele Delphi S2120.Additional Items I purchased separately:Miele Replacement Vacuum Filter SFAH30Miele Type G/N Hy-Clean Dust Bag
If you are going to buy a $500 vacuum you should be able to afford some replacement bags too. Since owning this vacuum I have only recently replaced the bag. We have 1 dog that sheds a lot and my wife has long hair that I find all over everything lol.
For example deep carpet cleaning vs. hardwood dusting.- The attachment wand telescopes, so one may adjust the length according to reach, comfort, etc.- This unit has an airflow indicator on the canister, indicating when a dust bag change is required.
The Miele filter bags hold more than expected, lasting longer than I thought they would; the dust and debris is also compacted into the bag. With the old Stowaway, the dust bin required emptying after each room. (We have three dogs... and LOTS of dog hair!) Now we don't have to empty the vacuum cleaner for weeks.
Answer: It uses the G/N bag. I don't buy the Miele bags as they are expensive. Through Amazon I buy the 3M Filtrete bags that are comparable and come with 5 bags and 2 replacement filters. These are thick synthetic bags to contain dust, dirt and allergens.