Series 86 block and tackle is built for sideload sash applications in both residential and commercial windows and is rated class 2 on the aama verified components list, the north american fenestration standard (nafs). Series 86 is designed to allow for quick and easy installation or removal of the sash. Part# 17b11-10, 12"channel length, id stamps 11-10, 11-1, 11-a