The innovative Treewear from GIBBON's is made out of Special-Felt and protects the bark and the line from abrasion. Velcro at the end of the Treewear makes it is easy to handle and prevents a slipping during setting up the Slackline.
These bands are a lot easier to use to protect the tree and your slackline than a towel, sweatshirt, etc... Does what it's made to do. Nice and durable. No complaints here.
These are a lot easier to use than a towel, but.... an old towel is free. If you want them, you will not be unhappy with your purchase.
I use two pieces of carpet scraps and they accomplish the same thing... I don't know if you need to spend money on this.