practice dunking. if you're sure that you can dunk on a rim of that height(whatever height it is ur trying to dunk on), then its all about practice. or maybe you just need those extra 1-2 inches. but if you're 100% sure you can get high enough to dunk, but just cant get the ball in the hoop then you need practice, eg. with a tennis ball first, and slowly getting used to a bigger ball etc.

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