BS1 or BSI Window Balance

Hello there! From what I can tell, it looks like your channel balance has side tabs, or 'wings', on the top attachment but not on the bottom. Is that correct? If so, I believe you'll need our Series 395 Channel Balance. You'll then need to determine the length of the metal channel, not including the attachments at either end. Based on the stamp this should be 27", so you'll need our S395-27. Finally, for a spring strength option choose 2640. Let me know if this looks right to you. Thank you!