Retort Bags vs Mylar for Canning

How does one know if they are buying actual retort bags designed for canning or Mylar bags not designed for canning? 

Although big companies have retort bags made in any size, color, shape they desire.  For those of us buying just the few hundred for our own personal use, there really is only one bag consistently on the market you can be sure is designed for retort canning.    It has writing on it, it is gold and comes in 2oz, 4oz, 8oz, and 16oz no gusset, a basic flat pouch.

All other products you should ask for the specs from the seller.  There are many sellers now a days pushing foil bags in all types and colors as retort.  The concern here is chemicals in the bags that will be released with the extreme heat.  Retorts are BPA and chemical free.  Also the air barrier properties of the bag will most likely be far less than that of retort pouches thus lessening the storage time and increasing the spoilage ratio. 

Be careful when you buy if the bag does not have the FDA printing on the bag ask for the exact specs and information certifying it as a retort cannibal bag before using it.