18" Gable Vent Octagon

PVC, Cedar, Cypress, Pine Octagon louvered gable vents.
The “stated size” is the “Rough Opening.”
Net Free Area: approx. 59.24"

The "louver box" measures 17 1/2" wide.

The overall outside of trim measurement:
with 3/4" x 2 3/4" SE "square edge": 21 ˝"
with 1 1/8" x 2" BM "brick molding": 20"

Standard louver box depth: 3"

Pictured: Rough Cedar with Standard SE Trim.