This is the SWISCO Series 751 Channel Balance Sash Support System (also known as a block and tackle balance) for tilt windows. When determining length, only measure the metal channel; do not include the fittings in this measurement. Used in windows manufactured by Kolbe as well as others.
The ribbed 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 15-014 shoe attached.
