A good night’s sleep in summer shouldn’t be a challenge. But many modern synthetic duvets don’t breathe – they just trap hot air. So we use all-natural down and goose feathers in our 4.5 tog summer duvet. Unlike synthetic fillings that simply trap heat, our all-natural goose feather and down-filled duvets are cool, soft and absorb moisture. Goose feather & down filling. 230 thread count down proof encasing. Hypoallergenic. Fill power 450.