M.2 SATA confusion

Etnies

I want to install a new SSD in my laptop (Lenovo u330p)

The connection on my motherboard is m.2 sata 2242 with "M" key. Meaning 5 pins, the ke,y then the rest of the pins.

Now all of the drives I can find are both "B" and "M" keyed drives.

I read this :

"A 'B' keying (pins 12-19) gives PCI Express SSDs up to 2x lanes of bandwidth, while a 'M' keying (pins 59-66) provides PCI Express SSDs with up to 4x lanes of bandwidth. Even with 2x lanes of bandwidth a 'B' keyed M.2 SSD still gives 10Gbit/s performance, whereas the 4x lanes on 'M' gives up to 20Gbit/s. M.2 SSDs with B+M keying maximize compatibility in both slots, and will operate with 2x lanes of bandwidth."

So why are all the available drives both B + M drives and not just M if M is better?

Etnies

Are you losing performance by this though? im guessing its not possible to just get M socket drives

ED E

M.2 is a connector, not an interface standard.

There SATA over M.2 and PCIE over M.2, the latter being much much faster (not that the SSD is too). More pins are for the more expensive PCIE SSDs I believe. Then theres also NVME on top of that.