Yellow = ABEC5, oil filled, shielded, steel balls recommended for relatively clean conditions. Schumacher On Road cars kit specification. Red = ABEC5, grease filled, double rubber seals, steel balls recommended for wet or dirty conditions. Schumacher Off Road cars kit specification. Orange or Grey = ABEC 5, oil filled, shielded, extra hard ceramic balls for higher efficiency. Recommended for On Road. Black = Pro High Precision German or Japanese manufactured, rubber seal. Recommended for Off Road. Metal = Pro High Precision German or Japanese manufactured, shielded. Recommended for On Road.