Considering what we see of them and how Ryoshu describes them, 'Omnipresent but unaware of each other,' I think they will only have 108 members. They seem to highly value information, secrecy, individual ability, and exclusivity. They also seem to lack ranks, unlike the other syndicates where rank is more important. They have that student teacher thing(oddly predicated by that one LoR Pinky mod that got everything else wrong by making them Zwei knock offs), but at least Zilu seems a full fledged member with a chuuni title and everything so even that seems to be semi-official at best.
With that said, they also seem fine with using outside resources, Lei Heng had infiltrated the Thumb and was probably using his position to advance the Pinky's Agenda against the Ring (Mentioned off hand in LoR), while Kong Qiu uses the Mao. It's pretty unique compared to the others who seems to use as much in-house stuff as possible. For instance, the Thumb have private Workshops and mind you Workshops are ran by Fixers so they have their own official Fixer organizations as well, not just ones they infiltrated. About the same probably goes for the Ring, Middle, and Index to vary degrees.
