What thread does the b-screw on a shimano rd-6400/6401 have?

I have in front of me an RD-6500, Ultegra 9s rear derailleur. The B-screw is an M4 x .75 pitch x 12mm length. Looking at a couple older shimano derailleur's, it appears that the B-screw is also an M4.

Shimano's website has various technical documents, some of which are "exploded view" diagrams of the parts that make up the part. At the bottom is the list of the parts, and when it's a fastener, they often give the size and length of it. However, the exploded view of the RD-6400 does not have the size of the B adjust bolt. Here is the EV of the RD-6500 which does list the B-screw as an M4 x 10mm.