These boards have been removed from mostly new MONITORS with broken screens and should work if properly installed. ACER EB321HQ MONITOR MAINBOARD 21201-00924 / 55T5MM6007. Please verify that your board part number is the same as 21201-00924 / 55T5MM6007. The part number is the first number left of the /, or the sole number listed. Most often written in title as (part number / board number)