This is the SWISCO Series 710 Side-load Channel Balance Sash Support System (also known as a block and tackle balance) for non-tilt windows. The series is determined by the combination of the top and bottom fittings attached to the metal channel. When determining length, only measure the metal channel; do not include the fittings in this measurement. Used in Acorn 3500 Series single-hung windows.
The metal channel's width is 9/16", but is considered 1/2" in the trade. It houses a spring and pulley system to raise and lower the sash and comes fully assembled with a 19-009 top guide and a 15-003 bottom shoe.
