Broan-Nutone Genuine Replacement Aluminum Filter For Range Hoods, 11-3/8" X 11-3/4", Fits Select Models Keep Your Range Hood Operating At Peak Performance With The Bp57 Aluminum Filter. This Filter Is Used In Ducted Applications To Capture Grease And Particulates Generated During Cooking. Replace Or Clean Your Filter Every 6 Months, Or More Often If Your Cooking Style Generates Extra Grease.