Hydrocollator® HotPac Set - Standard Set with Foam Filled Terry Cover and HotPac. Provides up to 30 minutes of deep, soothing, moist heat. One HotPac provides hundreds of cost effective treatments. Foam-Filled Terry Cover Features: For home or light clinic use - Polyurethane foam layer between two layers of terry -Washable and reusable. Superficial heating via Hydrocollator Hot Pac can elevate skin and tissue temperature within ¼" from the surface. If the treated area's blood supply is adequate, temperatures can increase within 6 to 8 minutes of exposure. Muscle temperature at depths of ½" to ¾" will require 20 to 30 minutes of exposure to reach peak levels. 100% cotton duck canvas material. Filled with bentonite. One year warranty. UOM: 1/EA.