Top window won't stay open, small plastic piece broke off .

Thanks for reaching out to us! The hardware you have pictured here appears to be the 15-181 Double Support Detent Clip, used along with the 15-182 Balance Bushing. This is typically used along with the 15-180 Coil Balance Shoe. I am confident this should be the replacement you need, but you’ll need to remove the shoe and compare the dimensions to confirm.

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This coil shoe is compatible with Series 190 Coil Balance Spring secured to the shoe using the 33-073 screw. To determine the correct springs for your assembly, you’ll need to remove them and check for any stamps/markings, this number will help you determine the spring strength you need.

If there aren’t any stamps/markings, you’ll need to obtain the exact weight of the sash. Once you have this number you’ll need to divide it by the total number of coils in the window. For example, if you have a sash that weighs 28lbs, you would need (4) of the S190-740 Coil Balance Springs.

If you need to replace the pivot bar, I suggest using the 26-040. Again, to be sure this is the correct replacement, you’ll need to remove the existing pivot bar and carefully compare the dimensions.

Alternate image for 26-040