Serene Foam Twin XL Size 4 Inch Thick, Advanced Supportive Air Technology Mattress Bed Topper Made in the USA Serene Foam Instantly makes any mattress more restful, comfortable, cooler and supportive in sagging areas of mattress 4 inches of soft yet supportive Serene Foam conforms to your body Made in the USA using enviromentally friendly processes. PURGreen Certified. Serene Foam reduces pressure points that cause you to toss and turn, so you sleep better. Topper features a Supportive Air Technology formula and a medium soft feel