ZoN Resistance Tube - Extra Heavy Resistance Compact and portable. Great for travel and home use. Break-resistant latex material provides consistent stretch. Available in four resistance strengths: Light, Medium, Heavy and (NEW) Extra Heavy. Ideal for resistance training, aerobic endurance training and rehab. Anti-sweat, high density foam handles provide a comfortable yet firm grip. Handles can be placed under the foot or around the ankle for a variety of exercises. Suitable for all fitness and skill levels.