That makes it important for bettors to know their horses and try to determine which one is most likely to overcome the handicap and win the race. The entry level Maiden Race circuit is the most common type of race in which weights are used to handicap thoroughbreds and make the field more competitive. Allowance races also use weight based handicapping, since many of the horses are around two years old and vying for a spot in the top levels of racing, where weights usually are not used but still appear in some prestigious events. Because horses are generally fully mature by age three, top thoroughbred races such as the Kentucky Derby, Preakness Stakes, and Belmont Stakes do not need to use them. Races run by younger horses at the top tracks are still often weighted to handicap the more physically mature horses and give the younger ones a better chance of winning.