2017 21.5-inch 4K iMac memory upgrade kit includes 32GB of RAM, tools to take it apart
Repair advice and spare parts supplier iFixit is capitalizing on the discovery that the memory and processor inside the new 21.5-inch 4K iMac can be removed and replaced, by creating a RAM upgrade kit that can allow users to open up their iMac and boost the memory up to the maximum capacity.

RAM from the 2017 21.5-inch iMac, via iFixit
In the teardown of the 2017 21.5-inch 4K iMac on Thursday, iFixit found Apple had used SO-DIMM slots for the RAM, instead of soldering the memory modules onto the logic board. This decision to make the memory removable may have been to allow Apple to install the user's requested RAM capacity at the point of sale, or to make replacing the memory easier if the iMac is sent in for repair.
The Max RAM Upgrade Kit from iFixit includes a pair of 16GB DDR4 2400MHz RAM SO-DIMM modules that are compatible with the new iMac desktops, bringing the memory up to 32GB. Apple currently sells the cheaper 4K iMac with options for 8GB or 16GB of RAM, while the more expensive model goes up to 32GB, leaving a third-party upgrade kit as the only way to bring the lower-specification version up to the higher capacity.
As noted in the teardown, despite being held in memory slots, the RAM itself is not meant to be a user-upgradeable part, due to the need to remove the back cover and other components to access the hardware in the first place.

In the kit, iFixit has included the tools required to gain access to the memory, following the repair instructions the firm also provides online. Aside from the memory, the kit includes a an iMac Opening Wheel, an iMac Service Wedge, plastic cards, a spudger, tweezers, four screwdriver bits, and a driver handle, as well as extra display adhesive strips to replace glue strips damaged as part of the procedure.
The iFixit iMac Intel 21.5-inch Mid 2017 Max RAM Upgrade Kit is available for purchase at $299.95, but the online store advises customers may experience a two to three day shipping delay. By comparison, it costs $200 to upgrade from 8GB to 16GB of RAM on all 4K iMac models, and $600 to move from 8GB to 32GB on the higher-priced variant.
The 2017 27-inch 5K iMac does not require a collection of tools or lengthy instructions to follow, as Apple includes a small hatch that users can open for accessing the memory directly.

RAM from the 2017 21.5-inch iMac, via iFixit
In the teardown of the 2017 21.5-inch 4K iMac on Thursday, iFixit found Apple had used SO-DIMM slots for the RAM, instead of soldering the memory modules onto the logic board. This decision to make the memory removable may have been to allow Apple to install the user's requested RAM capacity at the point of sale, or to make replacing the memory easier if the iMac is sent in for repair.
The Max RAM Upgrade Kit from iFixit includes a pair of 16GB DDR4 2400MHz RAM SO-DIMM modules that are compatible with the new iMac desktops, bringing the memory up to 32GB. Apple currently sells the cheaper 4K iMac with options for 8GB or 16GB of RAM, while the more expensive model goes up to 32GB, leaving a third-party upgrade kit as the only way to bring the lower-specification version up to the higher capacity.
As noted in the teardown, despite being held in memory slots, the RAM itself is not meant to be a user-upgradeable part, due to the need to remove the back cover and other components to access the hardware in the first place.

In the kit, iFixit has included the tools required to gain access to the memory, following the repair instructions the firm also provides online. Aside from the memory, the kit includes a an iMac Opening Wheel, an iMac Service Wedge, plastic cards, a spudger, tweezers, four screwdriver bits, and a driver handle, as well as extra display adhesive strips to replace glue strips damaged as part of the procedure.
The iFixit iMac Intel 21.5-inch Mid 2017 Max RAM Upgrade Kit is available for purchase at $299.95, but the online store advises customers may experience a two to three day shipping delay. By comparison, it costs $200 to upgrade from 8GB to 16GB of RAM on all 4K iMac models, and $600 to move from 8GB to 32GB on the higher-priced variant.
The 2017 27-inch 5K iMac does not require a collection of tools or lengthy instructions to follow, as Apple includes a small hatch that users can open for accessing the memory directly.
Comments
62 steps before you get to the RAM, including removing antenna cables, which I've found to be the most difficult part to reconnect on iPhones. Push a bit wrong and you've bent the connect and you're SOOL. Once you've gone this far, you might as well break out your pneumatic grinder and cut out your own access door for future changes. It's unfortunate the HDD is attached from the screen side so cutting another access panel won't work. (last two sentences sarcasm)
It appears iFixit is using Hynix RAM.
3) See #2.
I've performed some iphone repairs, most recently replacing the battery on a 5s, only to accidentally damage the TouchID cable in the process, permanently disabling it. Oops. Between that and the PITA of the tape strips, I'm done with that. (I used to build my own PCs as well, for decades. Done now)
The one exception is storage in portable devices. On a desktop you can just plug in an external drive and forget about it, but having to lug around extra storage with a laptop is a pain.
Storage capacity limits have gone up in five years while prices have dropped significantly. I may not be able to afford Apple's "holy shit" price for maximum storage when the computer is new, but maybe could when a third-party alternative pops up at a much lower cost a couple years down the road.
Maxing out storage on this 15" Touchbar cost me $1500! Wanna bet the same coin will buy 1.5-2 times as much capacity in a couple years? It would be really nice to be able to pop in a new, bigger (and maybe faster) storage device down the road.
btw, my 6 years old 2011 Mac Mini is still running like charm after 1 upgrade from 4 to 16 GB of RAM.