spring

Hello, thank you for posting,

It appears you have either our Series 351, with a 15-002 bottom attachment, or Series 390, with a 15-001 bottom attachment. Take a look at the image below and measure to determine which balance you'll need. 

The length of the metal channel excluding the nylon attachments should measure 25 inches long and you will need a 2420 stamp option.

Please review and let me know if you have any additional questions! 

Comparison of the S351 and S390 balance shoes.