USB Bitcoin miners are available to buy, but they don’t really generate any significant profits.
They’re a good choice if you just want to fool around with Bitcoin mining and miners like the Antminer S9, S7, S5, Antminer R4, SP20, and Avalon6 are too expensive for you.
You should buy one to learn how mining works, but other than that don’t expect much!
ASICMiner Block Erupter USB 330MH/s Sapphire Miner
The Sapphire Block Erupters were the first Bitcoin USB miners. They have 330 MH/s of hash power which would net you less than $0.01 per month.
It may be a good choice just to see how mining works, but like with most USB miners: do not expect to turn a profit.
GekkoScience Compac USB Stick Bitcoin Miner
The GekkoScience miners is just slightly better than the original block erupters.
Avalon Nano 3
The Avalon Nano 3 is a 3.6 GH/s miner, which will earn you about $1 per year. No fan is required and it just plugs into your USB port on any computer.
Bitmain Antrouter R1 Wifi Solo Bitcoin Miner
The Bitmain AntRouter isn’t exactly a USB miner, but it is similar. It’s low cost, but with that you get a low GH/s at just 5.5 GH/s which is a little over $1 per year.
The plus side is it works as a wireless router, so you can do some mining while providing internet for all your devices.