Yes Mike that is the size you need to tap into the collar of the Profi pipe.
Would be nice if they made that size with a 90 deg elbow in aluminum.
I do have a 3mm threaded elbow it just eats up too much area after you drill and tap
and its steel just flat out heavy.2.9g I have some 4-40 brass 1g but not an elbow.
In retrospect I have some aluminum 4mm a mere .6g
