Update July 15 2:39 pm ET: The regular Fire TV stick is now back in stock.
The Amazon Fire TV Stick is a little dongle that caters to 1080p TVs. And the Amazon Fire TV Stick 4K is a much more powerful device that's optimized for 4K sets. And for Amazon Prime Day, both devices are on sale at steep discounts.
Amazon Fire TV Stick: was $39.99, now $14.99 @ Amazon
The Amazon Fire TV Stick is a streaming gadget that lets you watch Netflix, Hulu, Amazon Video (of course) and just about any other service you can think of in full 1080p. It includes an Alexa remote, so you can find things to watch and interact with Amazon's assistant using your voice. View Deal
I reviewed both devices for Tom's Guide, and they both have appeal for videophiles. The original Fire TV Stick offers thousands of channels, and puts Amazon Video content front and center. If you need to make a secondary TV into a streaming powerhouse, it's a good, inexpensive choice.
The Fire TV Stick 4K, on the other hand, is a powerful device, supporting 4K resolutions, HDR color palettes and snappy menu navigation. Like the 1080p Fire TV Stick, this device also puts a huge focus on Amazon Video content, and requires a sometimes-inconvenient power adapter. But it's got a smart remote control, and offers a lot of power for the price.
Amazon Fire TV Stick 4K: was $49.99, now $24.99 @ Amazon
For 4K resolution, HDR color palettes and quick navigation through a variety of menus, the Amazon Fire TV Stick 4K is a good device at a great price. You can stream videos, listen to music, interact with Amazon's Alexa assistant and play games.View Deal
Both devices will be on sale until 11:59 PM on July 16, so if you want one, don't hesitate too long before pulling the trigger.