3/8" Shank Hex Bits?

Aug 22, 2016
A couple weeks ago, I was placing an order for various thing and there was a thread on this board about hex adapter sockets, so I found one offered by this retailer and added it to my cart. It was 3/8" drive which seemed to be overkill, but it was cheap. It is a Sunex 972423.

It finally arrived yesterday, and not only is it 3/8" drive but also has a 3/8" hex shank. I have the usual plethora of 1/4" hex bits and a few 5/16" hex bits in my impact screwdriver kit, but never heard of 3/8" bits.

I spent some time Googling last night and couldn't find anything at all outside of a few drill bits with a 3/8" hex shank. It seems like there must be some use for it since this adapter socket is manufactured, but I sure can't find it.

I just thought it was peculiar and wanted to see if anyone here would know something.

I want to say there were some older tool sets that had screwdriver bits that were 3/8 hex. Old craftsman or s&k stuff. I can’t remember where I have seen them.
You're sure it's 3/8" and not 7/16"?
After measuring, it appears to be 10mm hex. Right at .400”. The socket is normally available as part of a Ribe (similar to Torx for those who may be wondering) bit set.