SRF offers Kriya technique thru a mailed out hard copy.
Lahiri hard core followers will say that it must be given face to face. This makes sense as Lahiri himself gave individualized Kriya (based on possibly that persons abilities and current progress, I'm guessing here)
I wonder how effective and accurate the mailed out version is, for me.
One of the first questions we may ask ourselves is how possible is it to meet such people and to be in their presence for any amount of time? It is easy for some hard core followers to say such things as you mentioned because they are living in India near such people. i do not know how Lahiri's followers are disseminating Kriya today. Perhaps you do. It is interesting to me that you ask the question; 'I wonder how effective and accurate the mailed out version is, for me.' Only you will know and no one else.