window balance

I cannot tell by the manufacturer or label if this is the proper series. The stamp options signify different weight tolerances. Remove the window sash and place it on a scale.

26" Series 751 stamp options:

25r will carry a window sash weight range of 10 through 20 pounds
25hd will carry a window sash weight range of 20 through 24 pounds
25tg will carry a window sash weight range of 24 through 30 pounds

This information is based on 2 balances per sash. Balances are designed assuming friction in the jamb weather-strip will carry a portion of the sash weight. Suggested sash weights are approximate.