I bought this pad for a new cal king mattress we had just ordered, but had not taken delivery of yet.  The pad arrived very fast, before I had the mattress.  Now I am using both and am very pleased.  The pad is designed to accommodate a very thick mattress or even a mattress and topper.  It is actually a little larger than our new mattress, however, it does not move underneath the sheets.  

Pros: good quality, accommodates thick mattress, very comfortable
Cons: can't see any yet