If you've read through this whole buying guide and have a particular port or slot not covered yet, that's because you probably have one of the two outlier ports installed in your system: U.2 or mSATA. U.2 is rare in consumer PCs; it's mostly made with enterprise customers in mind. A U.2 drive like the now-vintage Intel SSD 750 Series connects to a U.2 port on the motherboard via a special cable, or to a PCI Express M.2 slot using a special adapter. These drives almost always come in the 2.5-inch form factor. Unless you have a U.2 port on your desktop motherboard you want to use, you can ignore them. (And even if you do, you can still probably hook up an M.2 drive.) mSATA, short for mini-SATA, is a predecessor to the M.2 form factor. It was primarily built into laptops, though some older desktop motherboards may have an mSATA slot aboard. With mSATA, the slots and drives use only the SATA bus, unlike M.2's SATA and PCIe support. For all intents and purposes, mSATA is a dead end, though you might run into it if you have an older laptop or desktop. Last of all is the "AIB SSD" mentioned earlier, which comes on a PCI Express expansion card, much like a small graphics card. Most use the HHHL (half-height, half-length) form factor, letting them fit into compact, low-slung PCs, and plug into the same PCIe slots you'd plug any other expansion card. You'd only want to opt for one of these, though, on a desktop PC that lacks an M.2 slot or a SATA port/drive bay you can use.