When replacing brake pads, one of the most important things to consider is the material the pads are made of. Common friction compounds include metallic, semi-metallic, ceramic, and organic. In most cases, the best type to use is the type that the vehicle came with. If factory pads were metallic, replace with metallic, if factory pads were ceramic, use ceramic, etc. All of the braking components, from the rotors to the calipers to the hardware, were designed with a particular material in mind, and will function best when paired with pads of that material.