Many models are designed to be frozen for cold relief. Common approaches include freeze-solid reusable ice packs, sealed liquid-filled or chilled stainless-steel roller surfaces that stay cold without leaking, and chilled roller balls that provide sustained cooling without creating a wet mess.
Product descriptions commonly indicate short treatment sessions of around 20 minutes after freezing. Several listings note that leaving the device in the freezer (often about 2 hours) yields roughly a 20-minute cooling/session time, with some items explicitly advertising 20-minute treatment periods.