Upon purchase, you'll receive TWITCH account.
Link it to your game account to claim the following items: 

1. Saryn Prime
2. AX-52 Rifle

NOTE: 
!!! Claim items promptly post-purchase; they may expire.
!!! Unlink the Twitch account once all items are collected.
!!! Items hidden after 6 months are still claimable.

You can only change the link once every 7 days! Keep this in mind if you have already linked today or are planning to buy several accounts at once.
Every 7 days you can buy and link a new Twitch account! You will receive all the listed rewards, even if you have received them before!