When I was checking out the after-market waterblocks on Amazon (for reference edition cards), I was happily surprised to discover the flow-bridge blocks (also made by XSPC) which are made to connect between the waterblocks, made for either 2 slot or 3 slot spacing.  I was glad to discover this, because it seemed like there may not be enough space to connect multiple gigabyte AORUS water block cards... meaning I probably will try to sell the one I have.
 
I would really love to have 3 (or 4) of the EVGA 1080Ti Hydro Copper (preferably FTW3), but I'm not sure how well it would work to connect them with tiny stubs of tubing and standard g1/4 compression fittings (obviously barb fittings would be too long, as the X16 and x8 slots are at 2 slot spacing intervals in my X399 Threadripper motherboard, if I recall correctly; unlike the single 3 slot spacing in my X370 board for my Ryzen 7).  
 
So the obvious question is:
Is there a similar water flow bridge, with appropriate spacing for the EVGA Hydro Copper cards?
I would strongly prefer to have OEM water blocks with their own correctly dimensioned water bridges, rather than having to install after-market ones on reference designs, just to make sure the water bridging is sound.
 
Any heads up on this?  Unless nVidia completely blows us away in late spring with their refresh, I would really love for a setup like the one described above:
3 or 4 EVGA 1080Ti Hydro Copper FTW3 in my X399 thread ripper rig, using precisely made water bridges at the correct (2-slot, in my case) spacing and for the specific dimensions of the water block...   Is this available now or any time in the near future?
 
Thanks.
 
Just FYI, This is for mainly for compute:  crypto & machine learning research & some data viz

Okay, thanks Scarlet_one.
 
I noticed you seem to have a quad GPU setup in your profile pic.
Is that a two slot spacing and what sort of connectors did you use?
Are those just regular pairs of compression fittings with a short strip of tubing?  ..thx
I was going to try my XSPC fittings, but they look kind of thick compared to the ones in the picture.
 
How have others connected their hydrocopper GPUs (1080Ti preferably) with 2 slot spacings?
 
I really hope I will not have to mess with the aftermarket gear on reference cards.
I already have all the water-cooling gear, pump/reservoir, tubing, fittings, radiators, high-static pressure fans...
but I ended up downgrading my first build to an X370 with Ryzen 7 air-cool, b/c my pump wouldn't fit in my case and the cpu wouldn't boot.
 
My threadripper build and the tedious, costly custom loop only makes sense if I use 3 or 4 water-cooled GPUs, but it's suddenly become a pain to get the parts, and I still haven't figured out what parts I need to bridge that many GPUs on my X399 motherboard (either Designare or ROG Zenith, will be testing the Designare on a new CPU before my Christmas return window winds up in less than 2 weeks).

Can use ek ftw3 blocks and there ek bridge.

A real pain to install and to remove the card afterwards haha.

You'll be installing the blocks together and lowering the cards down on the mb at once.

To remove is seriously fun as you'll need a long screw driver to unlock ea card from the pci-e slot and slapping a credit card under ea card to keep it from falling back into the pci-e slot and removing hehe.

@bcavnaugh  thanks, man.  It's great to know about that Aqua Link pipe option.
 
Unfortunately, I'm trying to link 3 or 4 water-cooled cards.
 
In my 2 GPU scenario, I think the spacing is sufficient and the case airflow good enough (Cougar 330? with 4 extra fans) that I can use air-cooled GPUs without running too hot.
 
In my X399 system, I really want the cooling performance of a custom water loop. (and hence not having to ever run fans at max perhaps)

@bcavnaugh thanks for pointing that out...  I do want an OEM water block like the EVGA Hydro Copper, the Gigabyte AORUS I have works and looks great in a well-spaced arrangement and comes with this massive, heavy copper block, but totally sucks at any hope of having quad setup.
 
In my upcoming water-cooled X399 thread ripper system (expecting replacement CPU this weekend), I hope to squeeze 4 GPU in my new Cougar Panzer Max case.  I have a 360mm rad and 280mm rad all ready to go.
 
But this means I need something like the EKWB setup or a good connector solution for the Hydro Copper...
 
Ahh AHowes' link might work with the Hydro Copper:
 
(without the https connection, as opposed to the http, the tabs links on the page won't work for me; I tell ya my network connection is jacked up (even though recently hard-wired), does it work with either connection type for you guys?) 
[the system keeps deleting my link to the product mentioned by AHowes which would potentially improve the utility of EVGA Hydro Copper... link was to 
Bitspower Mini D-Plug Set - G1/4" - Matte Black Finish
Model: BP-MBWP-C28
at performance-pcs com ]
 
What do you think of the Mini D-Plug in that link?  Has anybody actually tried it?  Would that do what we're asking for?

bcavnaugh
Good or Better Yet Great Catch on them items above
You can use any Standard G1/4" Fittings on the EVGA HC Water Blocks.
 
What are those connectors you use in this setup? Bitspower Matte Black Mini Dual G1/4" Adjustable Aqua Link Pipe (16-22mm)  
What are the dimensions?  barrel length?  Adjustable Length Range (16-22mm) Thread: G1/4" On Both Side
Do you think these would work with the 1080Ti Hydro Copper? YES (Two Slot Cards)
 
On this _removedlink_ I am not sure.
 
[changed http to https, b/c at least on my internet connection, the regular http page is broken (which may just be my connection, we have too many government hoodlums in my area]  ALSO NOT SURE ON THAT ONE, whups... PS the bot keeps deleting links.

Yeah the Cougar MX330 is an incredible case.  I just saw that there is one for $25.  They're practically giving them away, which is crazy, so ridiculously tempting.  For a no-optical drive, no hard drive system, two high-end GPUs, it's a really perfect box.  You can use the $100 saved for the GPU markups and some high quality fans.
 
But yeah thanks to both of you.  I think we've identified the needed component.
I think "Adjustable Aqua Link Pipe" is an effective search term.  I think the 16-22m length version should also work for the 1080 Ti Hydro Copper in adjacent double slot, such as in a tight quad GPU configuration, but someone needs to verify that.  Your picture shows that this fitting and size clearly works for the 980Ti Hydro Copper quad-GPU config.  I'm sorry that I overlooked that earlier.  For some reason, I only saw the other version, before you added the quad config.  Clearly we have a winning item.
 
There are also "male-male" connectors which might work, I saw one down to 5mm, not sure what sizes available.
 
The disadvantage of the "mini d-plug" suggestion by AHowes is that from what I can discern, it seems it is more likely designed to be locked tight when you bring the pieces together.  From what I can only guess, it appears to be a fitting where you can easily break apart a tube and put it back together.  It seems doubtful that it is designed to operate at partial separation, like the adjustable, sliding "aqua pipes", despite have the two sets of O-rings. It's quite a bit annoying that such a basic issue has taken such a big effort to resolve.
 
Now I have to wait for Hydro Copper to get in stock again...
One relief is that I realize upon studying the picture of the SC, SC2, FTW3 1080 Ti Hydro Copper, that they have 2 ports coming out top and 2 out bottom, but also 2 away from MB.  Worst case, this would allow an ugly patch up with tubes looping over, albeit probably only feasibly with the SC and SC2, because the taller FTW3 would have less space.
 
I wish I could prepay at MSRP somewhere.  Also:  since the FTW3 card is taller than the SC and SC Hydro Copper, keep in mind you can't use an aqua link pipe for those connections if you have to mix and match, but I suppose one could use those two outer ports between an FTW3 and SC2 Hydro Copper.

someone, should encourage Fry's Electronics to offer prepay on some EVGA 1080Ti Hydro Copper cards...
that would be much preferable over their current options
OR: more retailers should offer prepay.
 
Like, someone at EVGA says sure, we can make a flexible allotment to Fry's, just tell us your minimum commitment, and post us on your order book.
 
Just a thought.