This is from my Kino vinyl window

Let's go through the steps to identify your balance. Step one: Series. You need to compare the end pieces to our selection to tell which Series you have. Luckily for you, I can tell that those end pieces belong to either the Series 380 or the Series 385. You'll need to measure (as below) to tell the difference. The only difference is a single measurement of the shoe, where the Series 380 measures 1" and the Series 385 measures 1-3/32".

Step two is the length. You'll need to measure the metal channel and only the metal channel, from end to end. It probably will measure 27", so you may need a 27" balance, but you should measure and buy a balance that's as long as your metal channel, if it happens not to be 27".

The last step is the option, which determines how much window weight your balance can lift. To determine this, you can look at your 26 4 stamp and choose 2640 to match, but you should verify this number as well. Remove your window sash and weigh it. It should weigh between 19 and 26 pounds. Once you have the Series, length, and option, you can place an order online.