BUILDMART - 18" Plenum Box for [18" Linear Slot Diffuser - 3 Slot - Triple Slot] Premium Insulated Plenum Box for Heating and CoolingGalvanized sheet metal Plenum Box with foam insulation, ideal for Texas Buildmart 18" lineal slot diffuser. This air distribution box attaches directly to the supply of the HVAC equipment that heats or cools the air. Connects to: 10" flexible duct in oval shape. Can be used and brazed to a 4" or 6" wood stud. If you do not have this size flex, you can use a reducer to modify the size. Professional HVAC Installer is Recommended. Ideal for Texas

Neck: 15 3/4" x 9 7/8" - Face: 17 3/4" x 11 13/16"

18 x 4 18x4 4x18 4 x 18

CFM: 343 ft3/min - Effective Velocity: 9

Entry size: 2 entries of 10" flex in oval shape

Neck: 11 7/8" x 1 5/8" - Face: 13 1/4" x 3 1/16"

CFM: 348 ft3/min - Effective Velocity: 9

Mouth Dimensions: L: 71" W: 5"

36" X 3 1/2" Linear Slot Plenum Box - For Double Slot (2 Slot) Linear Diffuser - Texas Buildmart - Modern AC Vent Covers for Ceilings

Entry size: 12" flex in oval shape

ASIN: B07NF8LBBM

CFM: 255 ft3/min - Effective Velocity: 9

Neck: 25 9/16" x 5 7/8" - Face: 27 1/2" x 7 7/8"