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Amazon overhauled its line of Fire tablets late on Wednesday. The new tablets have updated screens, processors, and are running the latest version of Amazon’s mobile operating system, Fire OS 4, codenamed “Sangria.” Amazon is also introducing a new, unusually sized 6-inch Fire that will cost $99. And the company rolled out new Kindle e-readers.

Amazon’s entry-level tablet is the Fire HD, which is now two tablets: One that checks in at 6 inches and one at 7 inches. Both tablets have updated quad-core processors clocked at 1.5 GHz and a screen running at 1280 x 800 resolution. [company]Amazon[/company] used to leave cameras off its least expensive tablets, but this year’s Fire HDs have front- and rear-facing cameras. (Amazon is no longer calling its tablets “Kindle Fires”: They’re now just “Fires,” the way Amazon’s phone and streaming box are “Fire Phone” and “Fire TV,” and and only e-readers are still being called Kindles.)

The 7-inch model will still cost $139, and the new 6-inch version is aggressively priced at $99, although you’ll have to put up with Amazon’s ads (“special offers”) to get those prices (the ad-free devices are $20 more). There aren’t many tablets with 6-inch screens on the market — although there are a few phones with screens that size — and there are very few tablets from a major manufacturers retailing under $100, so it will be interesting to see whether the small and cheap tablet can spur impulse buys this holiday season.

Amazon VP Peter Larsen noted that the 6-inch device size isn’t really new to Amazon because it has been selling 6-inch e-readers for a long time and knows that customers like the size. He also said that the company has gained customer feedback — mostly complaints — about the sub-$100 tablets it sells from other manufacturers, and kept that feedback in mind when building the Fire HD. (One major complaint was that cheap devices break easily, and Amazon is stressing the Fire HD’s durability.)

Amazon has also updated its 8.9-inch Fire HDX. The Fire HDX 8.9 is Amazon’s most expensive tablet, so its improved specs should be very welcome. It’s packing a new quad-core processor clocked at 2.5 GHz. The screen retains its 2560 x 1600 resolution, but should have improved image quality due to a new feature Amazon calls “Dynamic Light Control” that makes a tablet screen more closely resemble a piece of paper for reading apps. The new Fire HDX will start at $379, the same price as its predecessor.

Amazon also announced Fire tablets for kids, called the Fire HD Kids Edition. The hardware is the same as the new Fire HD 6- and 7-inch versions, both with 1280 x 800 screens, and the same quad-core processors.

But they are also more expensive than the regular Fire HD. The 6-inch Kids version costs $149 and the 7-inch is $189. (There are no ads on these devices.)

Where does that extra expense go? Amazon is offering several nifty services with the Fire HD Kids Edition, including a “two-year worry-free guarantee,” which promises that if your children break the tablet you will get a replacement for free, “no questions asked.” That includes water damage, cracked screens and any random damage your kids might do to the tablet. The Fire HD Kids Edition includes a soft-rubber case (which Amazon also sells separately for $24.99). And with the purchase of the tablet, Amazon is also including a year-long subscription to Kindle FreeTime Unlimited, its all-you-can-eat library of kids’ ebooks, apps and games, complete with various parental controls.

Even though it’s clearly targeted toward kids, I can think of a few grownups who would love a cheap tablet with an ironclad insurance policy and rubbery grips.