The exact millimeter or inch thickness of the upper over-the-door hook portion for the Gerson 2310750 wreath hanger is not officially published in the manufacturer specifications, which generally state only that it is designed to fit standard-size doors. Standard over-the-door metal wreath hooks of this style typically feature a flat metal bracket thickness of approximately 1/16 inch (about 1.5 mm to 1.6 mm) to allow most residential doors to open and close without scraping the door jamb. However, if your door has a tight gap against the upper frame or weatherstripping, a standard metal hanger can cause binding.