So, here's my theory.
My first binder was bought from f2mbinders (dot) com. They are underworks, but the measurements will have a female instead of a male.
My second binder was from underworks men's section. underworks (dot) com
Even though I bought the same binder, they were slightly different. The men's lasted me much longer than the f2m style binder.
Both measure for a large for me, so yeah, the f2m binder is longer and the armpits are wider (this causes boobs to spill out) my main issue since I'm asymmetrical. One side sticks out from the front of my armpit, not pleasant at all.
With the mens underworks style the armpits are shorter and so is the length of the binder (about an inch and a half). Also the straps are wider.
I only order tri-tops.
So, if you did the same thing I did, yeah, they'll be different even though it's the same style binder. Weird, but this is what happened with me.
I ordered 1 new binder from underworks tritop. This is supposed to be the bio-guys binder.
Make sense?!