Balancers for aluminum window

Thanks for posting. It looks like that the metal channel, not including the nylon fittings on both ends, is 33" long. Please confirm. If so, this looks to be either an S380-33 or S385-33. The only difference between these two balances is the depth of the bottom nylon shoe, or the measurement from 'heel' to 'toe'. See the illustration below for reference. Compare both with your old balance to be sure what matches best. In either case for a new stamp option go with 3230.

Comparison of the S380 and S385 balance shoes.

The stamp code on your old balance indicates the weight range it's designed to support. 32-3 conforms to our stamp rating of 3230, which can support a window sash in the weight range of 18 through 23 pounds. If you want to be extra safe you can indeed remove the sash and weigh it to confirm it falls in that range. But unless you had issues with these balances before they broke, I think you can safely assume that S385-33 with a stamp option of 3230 is the right call. Let me know if you have further questions.

Hey Jo. A 30" balance stamped 29-30, or 2930, should support a balance in the weight range of 16 through 23 pounds. With few exceptions, you can disregard any codes on these balances besides the first three or four digits. Those other letters and numbers (like that '11' at the very end) are manufacturing information, the meaning of which can vary a lot by brand. And again, unless your window was not performing well from the beginning--either it was difficult to open or keep open, or difficult to close or keep closed--then you can assume the stamp option is correct, and therefore there's no need to get the exact weight. These balances are carefully calibrated to handle any weight within their designated weight range. 

Let me know if you have any other questions! 

My pleasure, thanks for the kind words, and thanks again for reaching out.