DS1817+ RAM Upgrade. Synology says DDR3L but you recommend 1600MHz not 1866MHz?

[Enquiries]

Compatibility list from Synology says the approved RAM for the DS-1817+ is RAM1600DDR3L-8GBx2
It says 1600, but it also says DDR3L.

You recommend Crucial 1600 DDR3.. But not Crucial 1866 DDR3L...

Which is the correct memory?
1600 DDR3? CT2KIT102464BF160B
or
1866 DDR3L? CT2K102464BF186D

Searching Crucial's website they say they don't make compatible memory.