Look for replacement for my old channel balance

Thanks for posting. This appears to be either an S380-27 or S385-27. The only difference between these two balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement. See the diagram below for reference. Compare both with your old hardware to see what matches best.

Comparison of the S378, S380 and S385 balance shoes.

You have to choose a stamp option, which designates the strength of the balance. A balance stamped 26-3 would conform to our stamp option of 2630, which designates a balance that can hold a window sash in the weight range of 13 through 19 pounds. 25 pounds is considerably heavier, and would fall under a 2640 stamp range (19 through 26 pounds). Please double-check the sash weight. If you've never had issues with these balances prior to them breaking--e.g., if the sash never had trouble staying closed, or getting closed--then it is probably within the 2630 range and you should go with that.

That measurement is deceptively important, yes. If the shoe is too small, your sash will wobble back and forth during operation. If it's too deep, the shoe will dig into the vinyl casing of the window during operation and could permanently damage it.

In your case, it's very likely the 1-3/32" version, since it falls between the two measurements. This is a common occurrence as they can wear down from friction over years of use.

Lastly, if you use a stamp whose strength rating is higher than the weight of the sash, you may find that the window is more difficult to close on average. In extreme cases it can also open on its own after being closed.