I’ve had Spring Air mattresses over many years – double pillowtop. There is one that has wool on one side and silk on the other and is called the “Four-Seasons.” It is very heavy to flip (esp the CA King) but should be flipped in the fall and spring with the correct side on top and top to bottom. It is very firm and will last for many years if flipped semi-annually.
This mattress might have different names depending on where it is sold but I believe the “Four Seasons model” is currently sold by Macy’s. Even the lesser Spring Air pillowtop mattresses are very good beds.
