Caldwell Window Balance

Thank you for reaching out to us. It's hard to say from these photos but I believe your top and bottom fittings have wings. With that in mind, I recommend you have a look at the S380-31 or S385-31. The best match will depend on the depth of the bottom fitting as shown in the image below. You will also have to select the 3030 strength option based on your 30 3 stamp. 

Comparison of the S378, S380 and S385 balance shoes.