I treated myself to this set on eBay. A few guys sell it, I paid £9.29 for my set including delivery from a different vendor. Good value and does the job very well under and above the playfield. The quality is more than adequate for the low torques required on a pinball machine. I have not tested them in a more challenging environment, but these will stay strictly for my pinballs as I have a draper expert socket set that I use more generally.
http://www.ebay.co.uk/itm/7Pc-SAE-I...605?pt=LH_DefaultDomain_3&hash=item1c2ce5524d
http://www.ebay.co.uk/itm/7Pc-SAE-I...605?pt=LH_DefaultDomain_3&hash=item1c2ce5524d