Our rectangular wall vents are 3.25 x 10 inch connections with a damper door and removable screen. They are made from 28 gauge alumimum and are commonly used for range hood or microwave ventilation. 3.25 x 10 duct transitions to 6 inch or 7 inch round duct. Range stack boot transitions are found at Lowes and Home Depot. Copper or Stainless versions of this vent here.