The Volas Mattress Topper is sold as a way to change the sleep surface without buying a new mattress.
A replacement mattress removes the old core. A topper sits on top. You still choose a listed size and White or Black. Those choices do not create mattress-level specifications such as thickness or a mattress warranty. Those are not on this listing.
If you want to keep the mattress, stay with the topper. If you want to remove the mattress, you are shopping for a different product.
Match the mattress you plan to keep on the Volas Mattress Topper page.