Window balance

Hey there!

Thanks for contacting us. My recommendation is the S351-28 or S390-28 depending on the depth of the bottom fitting. Measure as shown in the image below to see which one is the best match for your project. 

Note, the 45 at the end of your stamp may indicate the window sash weight. You can always weigh it to be sure. If it is indeed 45 pounds, you can use the 2780 strength option for your replacements. A pair of balances with such an option will support a sash weighing 42 to 45 pounds.

Comparison of the S351 and S390 balance shoes.

No, the part number won't change but you can select the 2780 option by clicking on the bubble next to it on the S351-28 and S390-28 store pages.