Interpreting Parts List
 

I have an easy question about screw sizes on the Porsche parts diagrams:

if it lists:
Tapping screw
B 4,8 x 16

I assume this is a 4.8mm diameter and 16mm length, is that correct? 4.8 mm seems bigger than the screw actually is. What does the B stand for?

if it lists:
countersunk-head screw
M 4 x 20

What does the M stand for?

Thanks

Tapping screws are self-tapping (Do you know Parker?)

4.8 is diameter in mm and 16 is length in mm

M stays for Metric and they are not self-taping (normal screws)

Thanks - for the fast response.