Looking for replacements for the 3"1 & 37" L 3/8" W balance

Thanks for posting! So what you're actually working with here are Spiral Balances. Spiral balances for tilt windows are distinguished by the length and diameter of the outer tube, as well as the color of the tip. If both sized balances are 3/8" in diameter, then you need an S900-31 and S900-37. You'll then need to select a colored tip option for each. I'm afraid I can't make out the colors in your photos, so feel free to send us closer pictures of the tips if you want to be safe. If you're uncertain, weigh the window sash for each set of balances. You can then match that exact weight with one of the weight ranges listed for each color tip option on the product pages. 

You are very welcome. We are glad to have helped you with your hardware. make sure and get back in touch with us to let us know how everything worked out. 

Hello! That looks like our 15-188. Look it over and let me know if you agree. I highly recommend removing it from the window to confirm that your dimensions match those we show on the 15-188 store page.

Awesome, thank you again! Please let us know how it works out.