Make sure you buy the right BP cuff, Dr Berry has a link on the video notes.

I'd previously just bought one that was 'well reviewed' and unfortunately it was before I was using FakeSpot...

I had a recent spike in my BP (one way or another) checked as high as 172/102 and so I saw my doctor. I checked out OK then so he suggested when I come back for my annual (a week and a half later) that I bring my cuff to calibrate / compare. Glad I did, we checked my BP on my cuff, and it was 155/108, then immediately checked it on his and it was 138/88. Glad to find, and will likely be replacing my cuff!