Genuine Original HP Slate 21-K100 21-S100 Series PCA Phobos All-In-One Desktop I/O Board 742590-001.HP Part Number: 742590-001Compatible Part Numbers: 010189P0B-35K-G 7900P0100A02H00Compatible Models: HP Slate 21-K100 21-S100 AIO SeriesPlease Note: Motherboards are part number specific. You must order by the exact part number of the motherboard you are replacing; this is required in order to avoid returns, delays and restocking fees. You can NOT go by the model or serial number alone! We obtain cross reference and compatibility information from the manufacturer (as well as other various sources); while we do this to the best of our ability, we do not guarantee its accuracy. If you are unsure, please check with your laptop manufacturer. Please order, based on the part number only!