Laptop memory

I'm not sure what exactly you want to do. From what I can see, you currently have 32 GB installed, two 16 GB Modules running at 2666 speed. Now do you want to add more RAM? If so, are you going to replace both modules with 2 x 32 GB Modules, or just one?

If you are going to replace just one of the two modules with 32 GB module, & that 32 GB module runs at 2400, compared with your current 16 GB Modules which run at 2666, then yes the speed of your remaining 16 GB module will also drop to 2400.

Memory speeds on the other hand normally won't make much of difference to the overall PC performance though.

I have to get the memory from https://eu.crucial.com

You have to get the memory from crucial?
You can't get Crucial memory through one of their resellers New Egg (for example) has inventory of faster compatible crucial memory in stock.

Over all (as mentioned above) the speed of your existing memory will lower to the speed of the slowest installed stick

Performance wise you shouldn't notice a difference. But later when upgrading it could come back to bite you

Example: You can't' get any more 2400mhz memory and have to buy a higher speed for more money knowing you're throwing money out the window because the faster memory will only be throttled back by the existing 2400mhz stick

Hi,

To clarify:

This laptop has 1 x 16 gig of memory in it with 1 bay free. Ive opened it up and see the bay free.

I want to add  1 x 16
So is this memory a good choice ? is it equal to or higher than the current spec of memory installed?
https://eu.crucial.com/memory/ddr4/ct16g4sfd824a

But according to the Lenovo Link you posted in your Question, both RAM slots are already occupied with 16GB each...

It is always best to match the 2 installed to be equivalent in their specs. If I were you I'd look for another shop that does have the 2666 modules in stock, or wait until your shop has them.

https://www.newegg.com/samsung-16gb-260-pin-ddr4-so-dimm/p/1B4-001D-005D9?Description=ram&cm_re=ram-_-1B4-001D-005D9-_-Product&quicklink=true

https://www.newegg.com/samsung-16gb-260-pin-ddr4-so-dimm/p/0RM-002H-00154?Description=ram&cm_re=ram-_-0RM-002H-00154-_-Product&quicklink=true

I opened up the Laptop and it has 1x16 and one free.  So at some stage x1 was removed ...

Ideally yes it would be good to have identical - this isnt an ideal situation. We keepexisting one and add 1 module

We are not buying from an alt supplier - It has to be Crucial 

Ive been told by a third party supplying us - Crucial say its compatable 

Im just making sure that memory doesnt clock down the existing memory 

It does clock down the existing RAM as we told you already. The original RAM will no longer run at 2666, but will be clocked down to 2400, it will run at the max speed of the new RAM, 2400. Besides that, the PC already has Samsung branded Memory, & not Crucial, so that alone would make it a better fit.

We are not buying from an alt supplier - It has to be Crucial ...
Im just making sure that memory doesnt clock down the existing memory

Yes it will

Hi,
Re rindi - "It does clock down the existing RAM as we told you already."
Apols Im multi tasking and missed that.

The original RAM will no longer run at 2666 - OK

... but will be clocked down to 2400 - yeah thats no good.

2400 is the rated clock speed, how is the RATED CLOCKSPEED PROVIDED BY INTEL not good (belonging to your CPU and chipset)?
I wonder what microchip masters degree you have to be able to contradict Intel's own specs?