hung windows balancer replacement

Thanks for reaching out! The piece you have pictured here is the 15-181 Double Support Detent Clip which is used along with the 15-182 Balance Bushing to support the coil springs. Each of these are used on the 15-180 Coil Balance Shoe.

Alternate image for 15-180

This support and shoe are compatible with the Series 190 Coil Balance, secured to the shoe using the 33-073 screw. To determine the exact coils you need, you'll need to remove them and look for any stamps/markings on the metal. 

If there are none, you'll need to obtain the exact weight of your sash and divide it by the total number of coil in the window.