517eb1a1_Toppers___BedBathandBeyond_com__What_it_s_for
[Mattress Topper Type] Guaranteed-to-Fit Mattress Pads [What it's for] 
Because it has a quilted top, a guaranteed-to-fit mattress pad helps make a bed feel more comfortable. It also offers better temperature regulation. The side panels of a guaranteed-to-fit mattress pad are made with an elasticized fabric that helps it attach securely to deeper mattresses, usually up to depth of 24". (These mattress pads are sometimes referred to as Tailor Fit or Expand-a-Grip.)
Buying Guide to Mattress Pads & Toppers - BedBathandBeyond.com
What it's for