Gold (HH): super-high friction, high heat (longer lasting) sintered bronze metallic compound with diamond ground surface for wet/extreme conditions (due to high heat generation, HH-Gold compound is not for Hydraulic/DH race use unless OE specified) Red (R): high friction, low heat (faster wearing) aramid based, semimetallic soft compound for DH racing Green: medhigh friction (medium wearing) aramid based, organic compound for XC/all-purpose (no squeal)