Reusable Therapy - 20"W x 34 7/8"L x 33"H Hydrocollator HotPac & Units - M4 Mobile Unit - 20"W x 34 7/8"L x 33"H Our largest unit has an extra-large tank with oversized drain. Requires 20" x 32" floor space. Includes 24 standard size HotPacs. Hydrocollator HotPac Introduces Improved Moist Heat Technology with New, Synthetic Fabric Here's an easy way to provide moist heat therapy for patients-quickly, easily and targeted to any point of the body. HotPacs provide up to 30 minutes of moist heat per session. And now, they have a new synthetic covering that helps resist mold and mildew, dramatically increasing their lifespan. You'll get hundreds of treatments from each pack.