Custom Air filter rack plenum,for filter 20x16x1",and 4 round collars 6"diameter

Other pictures are just for reference.
This
is a Custom  Sheet Metal return air filter rack plenum for filter 20 x 16 x 1″.
Made
in America by hand , housing 26 Gauge
. There is a 3/4″ hem flange on one 20″x16″
end
Outside
the plenum (around the flange) has dimensions 17-3/4 x 21-3/4″
and height 5-1/8″
,
and the other side is fitted with an end cap with a  4 round collars 6″ diameter
. Actual overall dimensions flange
side for this rack 17-3/4″ x 21-3/4″ .
From top to bottom the plenum is 5-1/8″ long and the collars
measures 4″ in length. There is a sliding door on the 20″
side for filter access. The door can slide from ether side allowing
for easy access. Filter for this plenum is 20 x 16 x 1″. Filter
is not included.