The Carlisle Brake & Friction HDB640 Series Service Brake is a hydraulically actuated, triple opposed piston, caliper disc brake designed for a variety of dynamic braking requirements. Both the caliper and disc requires fixed mountings. This brake provides a high torque range for heavy-duty service conditions. Multiple calipers may be used on a single disc to proportionately increase torque output. Most commonly used at the wheel location with 25 inch rims.