Watson Marlow 300 Series Pump Head Adjustment

How to adjust your Watson Marlow 300 series pumphead for different inner diameter tubing. This works for 313, 314 and related pumpheads. The adjustment can be done on or off the pump. You have to make the adjustment with the pumphead fully open so you can align the marks in the video.
Here's a close up photo of the adjustment.
photos.app.goo.gl/czgkH3RPiYf...