31 in 3030

Hello there!

Your balance is a match for our S351-31 or S390-31 but the best option depends on the size of the bottom shoe. Our Series 351 has a 1" deep shoe and the Series 390 has a 1-1/8" deep shoe so you'll need to measure as shown below. You will also need the 3030 spring strength option, based on your 3030 stamp. 

Comparison of the S351 and S390 balance shoes.

That would be printed on the metal channel. In your second picture in this discussion thread, there's a 3030 stamp which means you'd want the 3030 spring strength option.