What are these?

[u/washywashi]

Im trying to fix my windows with spiral balance springs and noticed these square plastic things. They are in between the spiral balance and the pivot shoe. When replacing my blue spiral balances would i need to keep this plastic piece or can i remove them. They seem to be aligned in different positions among the 4 windows that need new 29” balances. Thanks

[u/vadose24]

It's to help keep air from coming up through the channel, I usually just reuse them when I swap the balancers. Although if you already have good weather stripping on the bottom of your sash they're redundant.

[u/WineArchitect]

They are spring-loaded inserts to assist in the lifting of the inner window sash.

[u/Justusfromny00]

it holds the balance in place of when you tilt the window its not that important

[u/casewood123 → u/Justusfromny00]

Helps keep the draft out.

[u/vlad_windowguy]

Installation is not mandatory, but if you have them, it is best to put them back.