There are different styles of Select-a-Vent depending on the mold manufacturer or supplementary supplier.
Mine are like the above except there is a mix of mini and standard sizes on the same tree.
Westone has a rather different, shorter vent insert (see bottom of Westone page).
The acoustic and limiting properties of a vent increase as its bore size decreases and its length increases, so the narrowest and longest vent bore path in a mold predominates if it’s just one bore with varying diameter along its length (Dillon, 2012 Hearing Aids book).