Length Of The Extender
A lot of guys write that when they start out with an extender, they compare the length of the extender to his erect penis length. That is something that is irrelevant. It is the correlation between the compressed extender, ( when there is an extender that one can compress), and the length of his flaccid stretched penis - or - from the base of the penis and to the point just behind the head, ( glans), where the strap/noose is going that matters. For the guys that uses vaccum cup, it will be a different setup.
So - the erect length has nothing to do with it.