Balancer identification

Landlord from MO

Nov 14, 2025 4:54 pm

The only marking I find on the balancer it says 2820. It measures 28” inches long and 1/2 inch internal channel width. The balancer came out of a doble hung aluminum window. The main difference I see from the ones on the website is that this one does not have the tabs sticking out of the sides of the plastic piece.
The top plastic piece measures ¾” inches wide and ¾” past the balancer. The bottom piece measures 1 1/8” wide and it sticks out about ¼” past the balancer.

2 user uploaded images

4 Replies

Bob from SWISCO

Nov 17, 2025 3:36 am

Hello there. I am sure we can help, but first, can you double-check the metal channel length, not including the end attachments? Usually if a balance like this has a stamp of 2820, it would be 29" long. Please confirm and we'll proceed. Thanks.

Landlord from MO

Nov 20, 2025 10:08 am

I checked the length again and it is 28" long. It measures just under 29" with the plastic peaces

Bob from SWISCO

Nov 20, 2025 3:55 pm

Thanks for confirming. Most likely these metal channels were cut down to fit your window properly. In that case, this looks like either the S351-28 or S390-28. The difference between these two balances is the 'depth' of the bottom nylon shoe. See below, Measure your old balance's shoe depth to see what matches best.

Comparison of the S351 and S390 balance shoes.

You then have to choose a stamp option, which reflects the strength of the balance. Your old stamp we should assume is not reliable since these balances were modified. Weigh the window sash that these balances support. You can use that weight to choose the correct stamp option.