Fujitsubo Authorize R Gasket
 

Bolts from the mid pipe to the y pipe fell off and I lost the gasket. Does anyone know the size of the gasket or where I can get a replacement of that ring gasket or what I can use? I'd rather not have to buy a whole hardware replacement just for the one gasket. Thanks in advance!

Measure the flange and try looking through the Apexi catalog

To get the right size, you can check your car’s maintenance manual. For a replacement, enter a VIN on https://www.subarupartsdeal.com/and will help narrow down the options for the gasket you need, or you can try https://www.carid.com/ as well.