Andy M describes the pork tenderloin correctly. This is my photo gallery pictorial showing both pork tenderloins and pork loin cutlets with complete recipe variations learned from the best...
My Breaded Pork Tenderloin Sandwich Recipe Tutorial
I'm in the process of making my second annual holiday pork tenderloin sandwiches. The picture I posted was the first. I have them marinating in buttermilk overnight as we discuss. Tomorrow I will bread them with Japanese Panko bread crumbs and deep fry them. I found tenderloins nearly 3 inches in diameter. I'm still looking for a tenderloin capable of making a tenderloin sandwich the size I ate at the St. Olaf Tap in St. Olaf, Iowa.
Here is a movie I found that gives a couple of prep ideas for pork tenderloins that are not sandwiches but will show what a pork tenderloin looks like...
I should mention the discussion started as a pork fritter sandwich question. The fritter is what you think it is. It is a fabricated slab of meat from pork and is not a tenderloin. Low priced restaurants might have them, deep fry them and pass them off as tenderloins. I am not running across that very much. Also, some restaurants use pork loin cutlets. There is not a lot of difference but they will be a slightly tougher, less tender meat and a boneless pork chop a tad tougher, grainier yet.