As soon as I received this gel memory foam mattress topper, I aired it out for about two days and then immediately put it on our bed.  While it is hard to find mattress toppers that completely cover a California king size mattress this gel foam mattress topper fits the bill -- it completely covers the mattress.  No need to readjust it each time I change our sheets.  The gel mattress topper provides us with a very luxurious sleeping experience.  Also, I don't get as warm at night and we both sleep more soundly.  Definitely a great buy!