I buy most of my BB's (labled Prarie Farms all natural, cyrovaced packed) from a local grocery store chain and, recently, have been noticing, on some slabs, it is very difficult, if not impossible, to remove the membrane. I have removed the membrane on a bunch of ribs so am by no means a novice but on these ribs it just comes off in little pieces or not at all. It's like the membrane is extra thin and tears easily. The slabs are much narrower on one end than the other so am guessing they are from the rear part of the rib cage. Does anyone know if that could make a difference? I'm baffled.