I see these things at construction sites pretty often and have no idea what they are for.
It’s about 5 feet tall, 2 feet wide, 2 feet deep, 3-inch wall thickness and hollow. Big circular indents on each side. They’re usually empty, sometimes with random litter inside.
What is its purpose?
It probably pretty thin and easy to cut, makes it more universal since you can use it for any change instead of having to make specific ones for 90° turns or for T-junctions.