window balance

Thanks for reaching out to us. 2305 is a bit of an odd stamp. What we recommend doing is to weigh the window sash. There's a chart under the product description on the S380-24 store page that will help you determine which stamp option is best for the replacements. 

I would recommend the 2320 stamp if the sash weighs 10 pounds. A pair of S380-24 channel balances with the 2320 stamp will support a sash weighing 9 to 15 pounds. 

I'll be here if you have any other questions!