What are they made of? Simba - Odyssey November 22, 2017 17:26 Updated Follow Each of these products has a 70% duck feather and 30% duck down filling, lovingly encased in a 100% cotton cover. Related articles What certifications does the Feather & Down range have? What sizes do the duvets come in? How do I use my Simba Mattress Protector? Do we have to pay to trial the mattress?