Genuine Hp 21 screen all in one desktop pc ac adapters, can be found below, simply select your model of AIO (this is located on the back of your all in one personal computer) then select it below or if you know the specification of your old or broken Hp 21 all in one desktop power supply, then match below or simply search the Hp spare number from your power adapter and if still unsure simply email us and we will be happy to send you a link for the correct Hp replacement for you.