Double size gaps at the bottom
The single size is good for gaps, the double and I guess larger gaps at the bottom of the bed as there are no fasteners. I have had to sew poppers so that the duvet does fall out (even though it has an envelope finish). There isn't enough material to tuck the bottom under the mattress, which means you only have one option....popper the bottoms. I didn't need that extra job. Would have been better had they manufactured them with a button or popper, then you can choose if to use it or not!!!! Not sure how long they will last as the material isn't that thick.