Finally I have found a pair of flannel sheets that have deep enough pockets to not come untucked from under the mattress. I have a thick pillow top mattress and a four inch foam topper I added to it. I have struggled with finding any sheets that would fit and not slip off the corners. Not only are the sheets big enough, they are very comfortable too. They might not be as thick as my Northern Nights flannel sheets were but they do fit the bed and are warm and toasty when it is cool in the house. I did do something different this time, I read the washing instructions before washing them, I have to say if you follow the directions there is no pilling on the sheets and they come out of the dryer just as big as they went in, no shrinking so far. I would recommend these sheets, I bought a set for my guest room queen bed too as that has the 4 inch topper too and finding sheets to stay put is difficult even without the extra plush mattress. I would give these sheets 10 starts if I could!