Depend on products 
-  Foam density
-  Thermal behaviour (sleeping bag)
-  Anti-mildew / Anti-bacteria / Anti-acarid
-  Impermeability/repellence
-  Dimensions of articles
-  Carrying/liquid content capacity, weight of articles, etc.
-  Resistance to ripping, falling, scratching, etc.
-  Resistance to tearing of fastening points
   (eyelets, handles, straps, etc.)
-  Tapping
-  Compression
-  Ageing (UV, temperature)