Im so excited to have this king size, mattress topper! It feels like sleeping on a duvet! It helps my back and joints, tremendously! Alwyn Home, the manufacturer, has been proving themselves to be one of my favorites with no mistakes, at all! This topper is like having a new mattress! It has straps to keep the topper in place. 4 inches seemed like it wouldnt work, however,  its working perfectly!