Instruction: Generate an answer to the question by utilizing the information contained in the document.

Input:
Question: Can this upgraded brush be used in the XV-21 model? Thanks!
Document: I used this on my XV-21 Target Stores Edition. It was easy to swap out the old brush kit and makes a big difference. I have all hardwood floors and the original rollers made a loud noise. This is much quieter and more tolerable. It definitely picked up more dog fur. If you have a pet and wood floors, get this. I highly recommend the upgrade.
Turned our non-pet Neato into a Pet friendly Neato. Filter enabled much better suction of our Model XV-14 (Costco version of XV-11). Benson (our name for our Neato), also was a lot less noisy with the upgraded roller. We have all laminate flooring in our house, with three German Shepherds. Highly recommend this for an upgrade.
Brush is very easy to install. XV-11 works much better on the hard floor - less noise, like XV-21. I have not tested filter yet, but i think it should also work fine.
The pet upgrade is an excellent upgrade to the Neato robotic vacuum. It really quiets down the vacuum. And it picks up even more hair than it did before. Thank you Neato for having the upgrade so we could add it to our already great Neato vacuum. So much better than the Roomba that I had first. The only thing you could do to improve the vacuum is add a edger brush, so it could pull debris in from the base board.Keep up the good work Neato!!! !Neato XV-21 Pet & Allergy Automatic Vacuum Cleaner
Want to spruce up your Neato and give it a makeover?This Pet & Allergy Upgrade Kit is the perfect way to do it!Your Neato will run quieter with the new beater brush and your home will be cleaner.You WILL hear a difference with this new beater brush. It IS quieter!I have the Neato XV-21, and it comes with both brushes, the old style brush and the new style beater brush.The new style brush also gets up more off your floor.The new Pet Allergy filter is a serious filter!
The Good:  I bought this upgrade package for my XV-21 and I have been very happy. I honestly can't tell the difference with the filter, but the brush is very much ahead of the stock brush. The wire bristles for a much better job of digging into carpet fibers and removing dirt and animal hair. After a morning run through my house, the hopper is always filled to the max with dirt. I believe the rubber and bristle combo on this roller does the trick that rubber can not do alone.The Bad:  I think the price is slightly hefty, but the upgrade is worth the money in my opinion.
This is a much superior accessory than the paddle only beater bar that was originally shipped with this model. I would downgrade the Neato XV original appliance. They should have shipped this upgrade at no charge.
If u place your hand at the exhause of the vaccum, it blows much stronger now. This means more air flow and at faster speed which means better sucking power. At no expense of cleanliness, all dirt are still trap by the HEPA filter. I am amazed. :) Its a good buy to upgrade any XV-11 model. Only 1 complaint here. In the instruction b4 u use the new HEPA filter, u must upgrade to the latest software. Otherwise Neato will shout for help! this was not provided as instruction in the package.
My cat used to be a bit wary of my Neato, but not after installing this kit. Now, my cat doesn't even move when it comes towards him.It does pick up TONS of hair, so the brush needs to be cleaned every so often, but the noise reduction and increase cleaning power make it totally worth purchasing.
Next, it runs... not quieter exactly, but the sound is more pleasant - no more annoying flapping noises that the old brush used to make, especially on parquet and other hard surfaces. I can't say much about the HEPA filter performance - but I can say that it's not more difficult to clean than the regular filter (unlike the HEPA filter for my "large" VC, which is a pain in a certain body part which I better not mention publicly), and the only drawback is that it takes up slightly more space inside the dust bin.
Answer: I just looked up the XV-21 and it appears that it already has the upgraded brush.