Having a lot of IKEA gear at the house including faucets, I had to replace an aerator on a Dalskär faucet because it was limestoned to hell. It had a coin slot, which was meant as the way to remove it, but due to the amount of limestone, it broke to shits. Anyways, it seems to have some sizing that is rarely used (M18.5x1mm threading), and looking on the internet I found out its made by a company called Neoperl, and its called Caché TJ PCA. I found a replacement unit numbered 636165 (Identnummer) with the text “Caché-HC-TJ-male M18.5×1 B” and “Z.636.165” also, barcode 7612158414436. It seems to come from Germany. Anyways it fits the Dalskär unit, and without having tried, it also seems to work with the IKEA Ringskär faucet.