These days there are motherboards out there with three, four, and even five M.2 sockets. Most boards only have one or two, though. If you've got a need for a bundle of NVMe storage, something like the ASRock Ultra Quad M.2 card is probably what you'll want. This card is covered in an attractive brushed-aluminum heatsink parted by a 50-mm centrifugal fan. Inside, there are four M.2 sockets. The good folks at TechPowerUp got a close look at the card at CES, and here it is in all its glory.
ASRock makes direct comparisons to the similar Asus Hyper M.2 x16 Card. The differences in the two cards are subtle but significant. The ASRock product has a slightly larger fan, and it takes power from a 6-pin PCIe power connector. It also mounts its M.2 sockets differently—the Asus card mounts the drives parallel to the PCI Express slot, while the ASRock Ultra Quad M.2 has the sockets angled from the bottom.
Slide from ASRock, via TechPowerUp
The arrangement of the M.2 sockets is supposedly superior in that it minimizes trace distance from the sockets to the PCIe slot, according to ASRock. The back panel of the card has activity lights for all four sockets, and ventilation for the heat that four NVMe drives are likely to produce. ASRock includes thermal pads attached to the heatsink over the M.2 sockets. The Ultra Quad card also has a configuration utility to control fan speed.
It's worth noting that these cards will not work fully in most desktop motherboards. There's no PCIe switch on board, so your motherboard has to support PCIe bifurcation. That feature is common on the high-end desktop platforms, and indeed ASRock recommends the card as an NVMe RAID solution for Intel X299 and AMD X399 systems. According to TechPowerUp, ASRock expects the Ultra Quad M.2 to go for $70 when it launches.