Solo miners are small machines that point their hashrate at a single wallet instead of a pool. Every block they work on is a full-value lottery ticket: the odds of solving one are very long, but the payout would be the entire block reward rather than a share of it.
They are also the friendliest way into the hardware itself. Most sit on a desk, draw less power than a gaming PC, and run an open web interface you can actually tinker with - the Bitaxe, NerdQaxe and NerdOCTaxe boards are open-source designs built by independent assemblers, so the firmware and the schematics are yours to read.
Please Note: these are hobby machines, not investments. We quote no return on investment and no payback period for anything on this page, because at these hashrates there isn't one. Buy a solo miner to learn how mining works, to support the network with your own node, and for the bit of heat it gives back.