(under subclass 381) Apparatus in which at least a portion of the member is comprised of two or more sheets, or surface extending masses, in face-to-face relation, or in which the material of the member is comprised of physically interrelated layers of different characteristics.
SEE OR SEARCH THIS CLASS, SUBCLASS:
380, for a single filter bag with a wall folded upon itself, both folds being facially unsecured so as to form plural separating surfaces, or a chamber therebetween.
