Heat regulated and extremely lightweight this quallofil air 4 seasons double duvet with allerban anti bacterial anti fungal and anti dust mite treatment plus water repellent and stain resistant treatment will keep you comfortable all night longsynthetic double duvet a 175 gm duvet for the summer and another 300 gm duvet for in between seasons join the two together to form the winter duvet fasten with ties quality value for the filling made up exclusively of extra fine silicon