24" Milgard Channel Block and Tackle Window Balance

Hey Beau. Is the metal channel, not including the nylon attachments at both ends, 24" long? If so, based on the style of the attachments this looks like an S395-24. You'll have to pick a stamp option, which designates the strength of the balance. Since there's no stamp on your old balance, what you should do is weigh the window sash the balances support. You can then match that exact weight with one of the weight ranges listed alongside each stamp option under the product description on the S395-24 shop page. Let me know if you have further questions.