A bag structure of a thermoplastic film material including a method and system for its manufacture, said bag structure comprising front and rear bag wafts connected by side walls and having an open mouth top portion, said open mouth portion being characterized by having handles located at opposite end regions thereof, said handles being of two films as a result of being integral extensions of said front, rear and gusseted side walls; said bag having a bottom wall planarly extensible so as to form a rectangle with at least no substantial excess film outside of the bulk volumetric capacity of said bottom region of said bag. The bag structure can also be made without handles.