Not sure, but I found the post by ehaberdasher where he says Mastai is made by a conglomerate called SAITT:
Also, on the Benjamin shirts you can tell the fit by the model number.
Model: Tropea B115 is the slim fit
Model: Tropea B102 is the regular fit
These are listed under Details for each shirt.
Yes - we probably should make this more clear on the site, although I believe there are currently only 3 fabrics in the fuller B102 fit.