How to identify a Delta Opening RETRO Blower � Requires a Setback Plate

This is an illustration of what is referred to as a “Retro” Delta Opening 14-71 and some 8-71 - They Require our Setback plate - https://www.alkydigger.net/proddetail.php?prod=BFM-BB1002

Speeds up the air flow and makes it come out of the front, so you re-center the blower on the intake.