Our Extreme 4 piston caliper is a fixed 4 piston aluminum caliper. This caliper has been designed with features you will not find in other 4 piston calipers. Some of those features include Stainless Steel Pistons, Stainless Steel pad guides, off the shelf pads and anti-rattle clips and an internal dust seal to keep your oil seal free of debris. With its overwhelming success as a "Quick Change" replacement caliper for the 65-82 Corvettes, SSBC has developed many different applications with this caliper. With piston sizes ranging from 30mm to a massive 48mm and applications from BMW to GM trucks you can be assured you're getting the stopping power you need!