DDR4, yes of course. Not replaced, have sold everything. I was into the bench scene (LN2) and needed a break so everything went.
Those sticks i had had samsung b die on them, while fantastic for benching were not great as a 24/7 set up as they would cause instabilities if you ran them at there max 16GB, i had to set maxmem in windows to 4096mb to achieve those sort of results but they would fly!
To note, they were rated at 1.35v, i ran mine at 1.86v which is no bother for benching but not for 24/7 use