Which bag are you talking about ??
The BCA bag does not come with specific mounting hardware for the Polaris tunnel channel. Most guys will run carriage bolts but you do run the risk of doing some minor damage to the tunnel rail as some carriage bolts seem to end up pulling upwards.
The easiest fix is using the t-bolts from Polaris that hold down the rear seat bracket. There about 2.95,a piece from Polaris (local dealer was cheaper) and they fit and work great! Here's a link to the part number,
https://www.polarispartshouse.com/oemparts/p/polaris/7520464/scr-spcl-m6x1-0x20-8-8-zod
You will also need some nylock nuts and small spacer but those can be purchased at your local hardware store.