I need to replace 2 channel balances in a window where they were none. They are the S380 style. Weight of window is 11 lbs. Channel is 1/2 in. The actual window is 33 1/4 wide and 30 1/2 high. the cutout is 57 in high and 57 in wide. I have recently replaced several of these in the hast few weeks so I know what I am doing. Please advise me on the part.
Paul