Spring balance replacement

Greetings! It sounds like you've done your homework and are certainly on the right track. If both your top and bottom plastic attachments have wings, you can take a look at the S385-28 and S380-28. The S385 includes the 19-005 top and 15-004 bottom. The S380 had the same top attachment, but the shoe is the 15-005. The 15-005 has a depth of 1" while the 15-004 has a depth of 1-3/32" You'll have to measure yours to be sure you select the correct balance. From there, you'll choose the 2740 (to match your "17 4" stamp) option that supports the weight of your window sash. Let us know if you have any additional questions.