Window balance with "2830 BSI VE"

Question

Some of my windows' balances broke after about 10 years. Looking to replace them but find the naming conventions confusing.

From my understanding, the replacements should be 29".
The top and bottom guides are less clear.

The only marking on the units is "2830 BSI VE" as pictured.

Any help would be appreciated.

Bob · Accepted Answer

Hello there. This looks like it likely is an S390-29 Channel Balance. The only other possibility is the S351-29. It comes down to that bottom nylon shoe depth. See the diagram below. From what you show, the depth looks greater than 1", and therefore it's the Series 390. But pictures of measuring tape can deceive, so double check to be safe. For a stamp option, choose 2830.

Comparison of the S351 and S390 balance shoes.