Waterproof Mattress Cover and Twin XL 4 Inch Thick 4 Pound Density Visco Elastic Memory Foam Mattress Bed Topper Made in the USA Waterproof Mattress Cover to protect your 4 Pound Density Topper from spills and leaks 4 inches of extra supportive 4 lb memory foam conforms to your body perfectly for a more restful and restorative Sleep Made in the USA using enviromentally friendly processes. Exceeds PURGreen certification standards. 4 Pound Density Memory foam reduces pressure points that cause you to toss and turn, so you sleep better. Topper features a four-pound density and featuring a famous gel-like feel.