I use which ever is closest, which is usually impact(all my air tools are in one tool box along with the sockets) but i have used non impact. The air ratchets are non impact so if you're using a good qual non impact socket(craftsman, sk, snap on etc) i don't see any worry. as others have said you def wnat to use impact grade sockets with impact wrenches, if for no other reason thier increased mass helps to amplify the impact effect, not to mention safety reasons :) If you are looking, harbor freight has some nice socket sets, i have 3 of them myself. 2 sets of deepwell(SAE and MET) and then a std set of impacts that are both sae and met.
I will vouch for those Harbor freight sockets. Busted three good 6pt sockets on two differ cars of same model for same type exhaust job within 2 months (you would think I would have learned the first time) , don't have the sizes need in metric. go borrow buddies. very impressed with the thickness and strength of them. Reason I am stating Is Terrapin may be able to confirm this, is they are also a great price. Craftsmam like 60 dollars Harbor freight's like I think he said 12 bucks not sure.
Ben07
This message was modified Feb 25, 2005 by Ben07
Ariens 8524LE, Toro CCR2000, Jacobsen S-B S-blowers, Generac 10hp Gen-convt. to N.G., 5 L-boys(D's F's &Dura( 74,77,80,88,00), Antiq. 1960 AYP 20 in. mag w 3.5 Tech mower. Ryan/Ryobi gas Trim. AYP 205 gas blwr. Mac c-saw,Toro E-blwr, 2 Weed-E e. stg. trims. outboards, boats, util trail, 2 Jeeps
do I have to use impact socket's, it seems to me that regular sockets would be ok since it only delivers 45 ft/lbs of torque. 
