The Original Hydro collator Moist Heat HotPaCs Since their introduction in 1947, thousands of doctors and therapists have insisted on this classic heat therapy treatment modality. Eight Hot Pac sizes are designed to fit every body contour for use in heat therapy. HotPaCs are easy-to-use, just immerse in your Hydro collator Heating Unit, then remove and wrap in terry cover and toweling and apply to treatment area. Provides up to 30 minutes of deep, soothing, moist heat. Color-coded tabs on most HotPaCs for easy clinic rotation. Best of all, they are cost effective for heat therapy and provide hundreds of treatments from each Hot Pac.