I started using this a few months ago, I wore the Kat Von D Beauty Lock It Foundation and this always worked perfectly with it, it blended in seamlessly with my foundation and leaving no harsh lines. The primer itself is great, a little goes a long way, it dries down evenly and smoothly without creasing and provides the perfect base for your eyeshadow allowing it to blend seamlessly and show up more opaquely. I have recently switched to a new foundation, this foundation is a water based foundation whereas my KVD one was more of a mouse based foundation and with this new foundation this primer does not work at all!!!! It does not blend in with the foundation and leaves horrible harsh lines which are impossible to get rid of. While the primer itself is great I unfortunately can't use it anymore as it doesn't work with water based foundations which is such a shame because this was my favourite eyeshadow primer.