Hydrocollator® moist heat pack heating units heat moist heat packs in a water bath. SS-2 Hydrocollator Mobile Heating Units features high-quality stainless steel, thermostatically controlled temperature, 3? (8 cm) swivel-type rubber casters for silent, friction-free movement, easy maintenance. Simple to fill and drain. No plumbing required. mobile heating unit - M-2 with 12 standard packs.