These 13.5 Tog Goose Feather and Down Duvets give an excellent option providing you with three combinations.A 4.5 tog for those warm summer nights,a 9.0 tog to take you through spring and autumn,combining into a 13.5 tog for those chilly winter evenings.You have the best of both worlds with Goose Feather and Down Duvet,giving you all the benifit of a light filling with all the warmth you could wish for and all the warmth you'll ever need.