The ProFlex 6275 Reusable Hot\/Cold Pack Replacement (2-Pack) is compatible with ProFlex 1675 Back Support Brace and is designed to provide soothing pain relief on or off the job. The pack can either be activated in the fridge or freezer for cold therapy or warmed up in the microwave or boiled on stovetop for hot therapy. Cold therapy targets inflammation, swelling and muscle spasms, while heat therapy targets muscle pain, tension, stiffness and chronic pain. To install, slide the pack into the back mesh pocket of back support and secure in place using two button tabs.