What it is A plenum box (air handling component) used in HVAC systems. A plenum is a chamber or duct segment that serves as a distribution or collection point for air flow.

Manufacturer / Model “Green Metak Mfg” (likely “Green Metal Manufacturing” or a variant) is the manufacturer; model/type AHSB.

Size / Dimensions 17‑1/2″ × 11‑1/4″ × 36″. Probably width × height × length (or height × width × length) depending on orientation. So the cross‑section is 17.5 in by 11.25 in, length is 36 in (3 ft).

Shape Rectangular/plenum box. Usually rectangular with flat inlet/outlet, ends for duct connections.

Function in a system Likely used to distribute or collect air downstream/upstream of ducts, to act as a transition piece, possibly serve as inlet to filters/fans or connector between duct runs. May also serve to reduce turbulence, equalize flow, or provide space for dampers/controls.

Installed Location Inside HVAC systems—could be in ceilings, walls, mechanical rooms, above drop ceilings, etc. Usually in conditioned or semi‑conditioned space depending on design.