As the other reviewer pointed out, this pair of pant is made of thin material.  In fact, I'm not very sure I would call it flannel, more feel like regular cotton.  As sleep pant I think it's fine, as my home is not exactly the coldest room out there so I don't need a pair of particularly warm pant, but the material it's made of was indeed below my expectation.  Also I think it's single layer, unlike some sleep pants have another layer touching your skin.