This is a brand new rear left drum brake wheel cylinder, designed to fit select Toyota and Scion vehicles.
The part number is WC370146, and it's a private label product – meaning it's made to the same specs as the OEM cylinder but without the dealership markup.
If your rear brakes feel spongy, you're leaking brake fluid, or your drum brakes just aren't grabbing like they used to, this cylinder could be the culprit.
It bolts directly onto the backing plate and pushes the brake shoes outward when you hit the pedal.