More information, please.
Who is "they" and what purpose will the measurement serve?
Lost Sheep
Edited to add:
I read through many of your other posts on this forum and see that you have had a prostatectomy and are considering an implant. Your question, then appears to be. "How will the implant size be determined?" The measurement is of the INSIDE space of your penis, from proximal crus (pelvic bone) to distal tip (your glans, on the inside). Tissue structures can vary from individual to individual, so outside measurements are largely useless.
If what I surmised from your posts is correct, you may want to watch this video of Dr Kramer measuring a penis. The measurement is at 1 minute 50 seconds into the video.
http://search.myway.com/search/video.jh ... uCNmahAWXISince you have been using a vacuum pump regularly, you may have already done most of the preparation described in this paper.
http://file.scirp.org/pdf/ASM_2013012514045982.pdfThe protocol is daily inflation for 10 minutes and clearly demonstrates that benefits are available from use of the pump.
1) Retention of size
2) Ease of insertion (easier for the surgeon and less discomfort for you post-op)
3) Earlier first inflation and use
You have been using a vacuum pump already, but if you do a daily as described in the paper (see the excerpt below) you will duplicate the protocol mentioned in the study.
"The penis is placed in the vacuum cylinder and the device pumped to the point where the patient feels a slight burning. The constriction ring is not applied and the penis experiences the vacuum for at least at least 10 minutes. Patient compliance is critical ..."
I hope this helps.
Lost Sheep