The flannel stays flannel it doesn't ball up with use I love mine only thing, after washing and drying King set the first time the lint trap on the dryer was full and about 3/4" deep in lint, but sheets didn't look any thinner. They fit great on my 16" deep mattress, and now get this, the fitted sheet actually hangs over the side of the mattress about 14" on either side, able to keep thermostat down at night another plus