ENER-J Slumberdown Combi Polycotton All Seasons 15 Tog Duvet is made up of two separate duvets; one extra cool 4.5 tog duvet and one nice and cosy 10.5 tog. When clipped together, they make an extra warm and snuggly 15 tog duvet. Use the 4.5 tog for keeping cool on warm summer nights, the 10.5 tog on milder