Topper comes vacuum packed; opened package and allowed it to air out on a guest bed for four days; it puffed out really well.  However, there's not enough fill in the topper to be 4 inches thick nor luxury.  It does fit a king sized bed well and stays in place with elastic skirting.  First night sleeping on it felt soft but not plush as it does flatten down.  If you are looking for a down alternative topper for your mattress to soften your surface, this topper works really well.