A quick learner from Arizona says:
February 3, 2014
Is the stamp option necessary, and if so, how do I know which one is correct. I have a 31" and a 13", channel, actual measurements are 13.5, and 31.5
Tom from SWISCO responded:
February 4, 2014
Yes, the stamp option is one of the most important parts of balance selection! It determines how strong your springs are, and if yo don't choose correctly the windows will not operate correctly and the balances may even break.
The best way to determine what option you need is to weigh your window sash on a scale and compare it to the list of options we have for each balance in our inventory. We tell exactly what kind of weight each option can support.