After being so satisfied with my green medium carrier, I purchased my 2nd Sherpa carrier in a large since one of my pup has grown so much. The red one that has flaps that can be kept down for privacy and to block the cold air on the airplane floor.  If the pup wants or needs extra ventilation and visibility, the flaps can be rolled up and hooked to a ring on the handles.  It comes with a large side pocket for carrying collapsable bowls, treats and toys.  The material is of excellent quality.  When I had both carriers, the green and red,  on the floor last night my pups jumped from one to the other.  They love them both, and I do, too.