I bought this for an insert for a duvet cover I've had for a while.  I thought I'd be able to fill it with something I already had, but everything was too small.  This insert is too nice to be just an insert!  I'm using it for that though, because it fits just perfectly.  I sleep in a cool room, so this is the perfect weight and warmth for me.  Very glad I found this when it was on sale: on a fixed income I have to shop carefully.