I bought this RAM Kit for the newest iMac 5k 2020 (i7 10th gen) and the RAM Kit does NOT work! I tried different slots and even with just one RAM slot it was not possible to get the iMac to boot.
I would highly recommend not to buy this kit until someone has rejected my statement.
It works perfectly with my 27-Inch 5K Retina Core i5 3.7 GHz which I bought new from Apple earlier in 2020, although I think technically it's a 2019 model (iMac19,1). Hope that helps!