Window balance

Thanks for writing in. I believe we can help, but I'd like to confirm a few details. First, can you tell us the width of the metal channel? It should be either 1/2" or 3/8". Secondly, can you obtain the exact weight of the window sash that this balance supports? We will do our best to narrow this down from there. Many thanks. 

Thank you. If your metal channel is 3/8" wide then my top recommendation is the S800-29. This is the same size as yours and I believe the configuration looks to be identical, as well.

The only thing I'm not sure about is the stamp. "288 c" is very odd. I'm wondering if it might have read "28B" instead. Either way, the only way to be sure is to weigh the sash on a scale. You can see a chart on the S800-29 store page that tells you exactly how much weight each option supports.