vadeer--
6-8 inches is an awful small tree to climb. I believe that most climbers minimum is 10 or 12 inches. My API is 12 and my equalizer 10...or the other way around...I'm not sure. If you found one that would climb that small of a tree, I would recommend securing it to the tree with a ratchet strap once you get where you want to be.
Good luck,
Craig