Return air filter plenum, 12×20 with end cap, and round 10″ collar , hvac duct
There is a sliding door on the 12″ side for filter access. The door can slide from ether side allowing for easy access. Standard air filter 12″ x 20″ x 1″. Riveting, versus spot welding, provides a more durable bond resulting in a longer lasting rigid part that will serve you for decades.