Kids/Childrens Thomas the Tank Engine Bedding Duvet/Quilt Cover Set (Twin Bed) (Blue) Please note: This product is a UK import, this duvet cover supplied is slightly smaller than the standard US duvet size, it will fit but the duvet may fold at the edge when covered. This is not a comforter but a cover for a duvet. Official Licensed product. Quality Bedding Set. Size - Duvet cover: 53 x 79 inches.