Pella window balance boot broke off
Thanks for writing in! Your channel balances remind me of our Series 795 Channel Balance. If you are only looking to replace the shoe, our 15-195 1-1/4" T-Lock Balance Shoe should work well as a suitable replacement. Although, you may want to remove the shoe and compare the dimensions to confirm that it is a fit.
Should you decide to replace the entire balance, you'll need to obtain the length of your metal channel and confirm the type of attachment at the top of the balance; the top attachment will either a hook or a screw-in clip. If it is a hook, there is a chance that our 26-200 Balance Screw Plug could work for you. However, if the installation hole at the top of the window channel is not square in shape, you'll need a custom assembly.
The last piece of information you'll need to confirm is the stamp from the metal channel of the balance. The stamp is what indicates the weight range your balances should be able to carry to support the weight of the sash. You'll need this to select the stamp option.
For an idea on how to remove these from your window, take a look at the video below, starting at the 3 minute and 13 second timestamp.