You should think about 3 things when you buy a slackline:

Length
Width
Stretch / Bounce

Length

Choosing the length is easy. Most lines are either 15 or 25 meters. This is the maximum length, or span, that your slackline will cover. So a 15 meter set can be setup between 2 anchor points (trees, poles, posts etc) that are up to 15 meter apart. Being the maximum span, you can also setup a slackline or anything shorter.

Width

The width of the line/webbing is 25mm, 35mm or 50mm. Most lines are 50mm. The width does make a difference to the difficulty, with the wider lines being easier to walk on. The wider lines are also more comfortable under bare feet.

Stretch/Bounce

The less stretch or bounce the line has the easier it is to learn on. Our Slacklineshop NZ or Gibbon Classics will typically have the least amount of stretch whereas tricklines such as the Andy Lewis and Slammina will have the most.