CoreProducts uses bentonite clay in its exceptional hydrocollator moist heat packs. How clever to have included clay as part of the fill in this clover–shaped cold pack. Compared to other cold packs I have used (that relied on plastic bead or rice technology), this pack (primarily because of the clay) has superior mass (bulk), superior "mold-ability" to the body, and a softer interface with the body. Couple this with an innovative geometry - and an outstanding, frost free, cover [that doubles (on the dark blue side) as a Velcro connection] - makes a very impressive product.