Determining Replacement Channel Weight Rating

Question

I need to purchase two 30" replacement channel springs although I am having trouble determining the weight rating of the existing channels. Please see the images attached showing the ends and the ONLY numbers stamped on the channel. The metal channel measures 30" (not including the plastic end pieces) although one of the stamped numbers says 29... not sure if that is supposed to indicate the length.

User submitted photos of a window balance.

Tom · Accepted Answer

"29 3" usually corresponds to a 30" 2930-option balance. You can check that by weighing your window sash. Sometimes the old marking on the balance isn't accurate. For the S385-30 you picked out, the 2930 weight range would be between 16 and 23 pounds.