StopTech Anti Knock-Back (AKB) springs are designed to be placed behind the caliper pistons to reduce pad knock-back caused by hub or upright flex during hard cornering. This ensuring a consistent and firm brake pedal feel. This specific spring provides 4 lbs of force and is compatible with piston sizes ranging from 26mm to 36mm. Package details: - Item: Anti Knock-Back Spring (Sold Individually) - SKU: 42.200.1007 - Force: 4 lbs - Compatibility: 26mm, 28mm, 30mm, 32mm, 34mm, 36mm pistons - Material: High-quality spring steel Note: For a complete axle or caliper overhaul, ensure you order the required quantity based on the number of pistons in your braking system.