Window channel balance question

Question

Hi, my stamp says W2640, while I think I have narrowed down the series to two possibilities, I am not confident as to whether it is series 390 or 351.

Are you able to help based on the picture?

Thanks,

Bob · Accepted Answer

Thanks for posting. The difference between the Series 351 and Series 390 is the bottom nylon shoe, as you can see in the illustration below. A stamp of 2640 would indicate you need a 27" long balance, but double-check to confirm. Let me know if you have further questions.

Comparison of the S351 and S390 balance shoes.