https://www.homedepot.com/p/Armor-Door-36-in-x-80-in-Fire-Rated-Gray-Right-Hand-Flush-Steel-Prehung-Commercial-Door-with-Welded-Frame-Deadlock-and-Hardware-VSDFDWD3680ER/207153513
90 min fire rate. 在questions 里search core. 厂家回答就是honeycomb core纸的
Honeycomb core doors, known as (Hollow Core), are manufactured by using a pattern of fibreboard or cardboard to fill in the spaces between veneers to deliver uniform structural support. These doors are a perfect alternative to solid core timber doors.