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http://eu.ironman.com/triathlon/news/articles/2016/02/ironman-rules-q-and-a.aspx#axzz4DQo7wCDH
We increased the age-group draft zone from 10 meters to 12 meters for all IRONMAN 70.3 and IRONMAN events, including their respective world championships. The professional draft zone will remain at its current 12-meter distance. The draft zone distance will continue to be measured from the front wheel of the leading athlete to the front wheel of the following athlete; roughly equal to six bike lengths of clear space between athletes. The time allowed to pass another athlete will increase from 20 seconds to 25 seconds.
I was assuming 7m based on this