A slackline is a balance beam in the air - which improves balance and core strength. This kit also includes a bonus 50-foot teaching line that helps balance while mastering the skill. Attach the slackline to two healthy trees, 50 feet or less apart; easy-to-follow instructions included for getting this puppy ready for use. Ages 5+, 400 pound weight limit. And, yes, it's definitely a thing these days.