Difference between Series 380 and 385

Can you tell me what the difference is between the 380 and the 385 series? I see the shoe has different numbers but they look the same in the picture. Mine are stamped 1720 and are 17 3/4" long. I need 4 of them. Thank you, Bill.

Do you think 1/4 of an inch would make a difference?

Thank you for explaining the difference with the series 380 and 385. I measured the longest edge of the shoe and measured 1 1/16" so I'm assuming I would need the series 385. I am only replacing one bottom winged shoe but was going to purchase a couple just in case. My next question is how do I replace them in the balance if mine are held in by rivets? Thanks again for all your quick help. Jeremy

Thank you for your advice about measuring the shoe. Here's a bit more detail about where to measure, which worked for me:

The bottom of the shoe has a long straight section, then angles and curves up to form a rounded "toe" facing the window. I measured from the point of the "toe", parallel to the long straight section, to the other side of the shoe. In my case, it was 1 3/32", and the new sash balance fit perfectly.