i'm not holding my breath that it'll work well, but we'll see i guess. there are 2 types - 'normal' and 'hard'. i ordered the hard. the shaft extends as well as contracts. i plan to order a pair of 5955's, and don't want to blow those out very often (even though they'll be much tougher than the 645. at least the 5955 on my eXT8 is tough).
we'll see. it could very well be something that ends up in the toolbox, lol.
a little animated how-to at the bottom of the page -->
http://www.junfac.com/shop/index.php...roducts_id=184