Didn't think this would be as good as they said, but it was.
Easy to work out. Placed in 4 feather pillows (which helped keep the bag open ready for duvet) then put in a double feather duvet and another pillow. Seconds later air sucked out and all the above reduced into the storage container.
It could have easily taken more but I didn't want to mix feather and hollow fibre together for labelling purposes.
I have just ordered another one for the other 2 duvets and pillows and think I might even get a third for my summer/winter clothes storage.
Quite good fun watching the stuff shrink! Very pleased with this product.