This spiral tilt balance is constructed of a mill-finished metal tube measuring 9/16 inch in diameter. The FH series spiral balance features 2 available rod extensions; one measures 3/4 inch and the other 1-3/4 inch The colored nylon bushings of these spiral tilt balances indicate their spring and sash weight for which the balances were designed: white = standard (12 pound safe weight); red = medium (25 pound safe weight)and blue = heavy (35 pound safe weight) and black = heavy-duty (50 pound safe weight) . These spiral balances are used on vinyl single hung tilt windows.