For GLA and GLA-V2Allows for a greater range of gear ratios5000~5500KV  try ~6.5 gear ratio, recommended power for racers at small/medium tracks7000~7500KV  try ~7.5 gear ratio, for expert racers at large tracks9000~9500KV  try ~8.5 gear ratio, when you just want the fastest car...GLA-005