We've abused the Harbor Freight one on our IR 3/4" impact and unlike most of the **** in the store it is actually never showed any sign of twisting. I'd recommend giving HF a try on this item.
I've been impressed with the Harbor Freight impact extensions. I'm sure the Sunnex are great but I think you'd like these also, and they're Taiwan not Chinese. http://www.harborfreight.com/catalogsearch/result?category=&q=impact+extensions
Our local farm stores sold them in the 80's and we still have several open/boxed wrenches all marked "Japan". Above 9/16" they were pretty decent but the smaller ones would bend if using the boxed end and the open end would be unusable after one tough fastener.
Just grab a steamer at your local discount store and life will be good. I messed with the razor blades, chemicals, etc. for hours and was getting nothing accomplished. Steamer did all the windows in under 15 min.
Here's the Gearwrench set from Cripe equivalent to one that started the thread and it's $34
http://www.cripedistributing.com/gearwrench-metric-universal-impact-socket-84905-p-7744.html
I hate to be the one that tells you but I've had many different Leatherman tools since 1988 and they've all been magnetic. Hmm, does that mean they're ****? I don't think so.
I've had a 7/8" Bonney explode on me while tightening a hydraulic fitting. The flying ear cut my arm pretty deep to which I still have a scar. The v-notch Bonney wrenches were beautiful but the open end is prone to breakage.