New Mattress Safe Softcover Stretch Knit Box Spring Encasement Twin + Bed Bugs, Allergies, Waterproof Made in the USA Mattress Safe® Stretch Knit Box Spring Encasement with the patented “Zipper with the Hook”®. A sewn in loop and zip-tie is included to ensure tamperproof encasements. Fits up to 9" deep mattress. Bed Bug Certified Breathable Fire Retardant: CFR Title 16 Part 1632 Impermeable to Bed Bugs and Dust Mites Patented "Zipper with the Hook"® Plus+ Advantage Made In USA Ships from pet friendly non-smoking home