How to identify SBTPG tax refund: Is this "Immediate Response Requested" envelope from DC my refund check or card?

Filed my taxes and got approved. I see SBTPG (Santa Barbara Tax Products Group) showing up in my transcript but I can't figure out if they're sending me a check or loading it on a card. Been waiting forever and just want to know what to look out for in my mail. Today I received something in the mail marked "PRESORTED FIRST-CLASS MAIL US POSTAGE PAID" from "PO BOX 98285 WASHINGTON DC 20090-8285" with "Immediate Response Requested" and "Do Not Bend" written on it. It also has "Member FDIC BANK" on it. Is this my tax refund? Is this from SBTPG? I'm confused because I was expecting either a direct deposit or maybe a check, but this looks like it might be a card. The envelope says "IMMEDIATE RESPONSE REQUESTED" which makes me think I need to do something with it rather than it just being my refund. Has anyone else received their refund this way through SBTPG? Should I open it or is this something else? I've been checking my transcript daily and just want my money already.