I originally got the 4 inch, and that was WAY too large. I switched to the 2 inch and it is heaven. I haven’t left bed all day. I already noticed a difference with keeping me cool and more comfortable through out the night. Although I’m not totally cool, which was a little disappointing. But it did make a slight difference regulating my body temperature. 

Only thing I would say, is get some large sheets. A couple fitted sheets of mine will no longer fit well on the bed.