We bought this for our California King size mattress which does have a double-sided pillow top. I did expect a potential issue due to how deep our mattress is but the fitted sheet was horribly crooked (stitching). It would fit on a regular king mattress correctly. We ended up having to cut/tare the fitted sheet to even get it on our CK mattress until we could order a better set of sheets. I will say the quality of material was nice and the flat sheet and pillow cases were fine as well.