Alenco window balancer, 28 inches long with 5/8 channel width

Hello there!

Based on what I see in these photos, you have either the S380-28 or S385-28 channel balance. The crucial difference between the two Series is the depth of the bottom fitting as shown below. You will also need to select the 2730 spring strength option based on the 27 3 stamp. 

Comparison of the S378, S380 and S385 balance shoes.