{HEAD ~ The support system} is formed using less plastic and requires {TAIL ~ less stringent tolerances} than heretofore known while providing sufficient rigidity to the components of the window assembly to form a window assembly unit that is relatively easy handle and, further, less costly to manufacture 
requires
{ HEAD ~ The support system } is formed using less plastic and requires { TAIL ~ less stringent tolerances } than heretofore known while providing sufficient rigidity to the components of the window assembly to form a window assembly unit that is relatively easy handle and , further , less costly to manufacture
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