This product is a charge to modify your ceiling kit order to accommodate fan or A/C cutouts so that you don't have to make them yourself. Please note: Cutouts are an industry standard 14" x 14". You are responsible for making sure your zone selection and cutout dimensions are correct. Step 1: Select number of cutouts needed Step 2: Enter Cutout Zone Step 3: Enter front measurement Step 4: Enter rear measurement MEASUREMENT GUIDE: Click the title hyperlink to access measurement guideZONE MAPS BY VEHICLE: MB Sprinter 144 MB Sprinter 170 Transit 148 Promaster 159 Note: If you have a Transit or Promaster extended, the guide for the standard will work just fine. while the number of zones may be different, the measuring and zone specification methodology is the exact same. Always assume the front zone is zone 1, and count back from there.