Product Features Package includes all the hardware kit you need to install a sliding barn door. Except for doors (NO DOORS). The barn door hardware can be used both inside and outside. It is rustproof, waterproof, and fireproof. The standard door thickness for our hardware is from 1'' to 1 3/4''. If your door thickness is not within that range, please go to our second tab called "Customization Services" for more detailed instructions on how to customize it. The spacing between each hole is American Standard 16''. Tracks 7.5ft and under are one single track instead of being connected by multiple shorter tracks. Tracks 8ft to 16ft will be connected by two tracks. Tracks 18ft and 20ft will be connected by three tracks. Therefore, the spacing between the holes in the connecting section may not be 16''. The minimum clearance (from top of the door to the ceiling) you need to install this barn door hardware is 6''.