Top positive review
Mount the Doorbell Pro first, then come back and buy this if needed.
July 21, 2018
I ended up returning it, as it was not necessary in my installation. However, if you do need it, here's some thoughts:
My doorbell is perpendicular to the front door and perhaps 5-6 ft away from the doorknob, pretty close. The extremely wide FOV made angling the Doorbell Pro unnecessary.
The Doorbell Pro allows you to draw on the screen areas where you do not want motion sensor active. This means, you can use these shims to bias the Doorbell Pro towards the sidewalk, and still "zone out" areas that would cause a lot of false alerts (like cars going by on the street). You may also need to buy this to eliminate areas of undesired motion too.
NOTE: photo is deliberately cropped, so you are not seeing the entire frame.
I wish I had known it would be 2/3 the purchase cost to return it. (I should have checked.) I suggest if you are unsure, install the DB Pro for a few days and assess. Then place an order for these shims if you find coverage unacceptable.
Not shown are some screws included. IMO they are long enough for perhaps two plates (30° angle), but not long enough for all three shims (45°). They have some info on how long those other screws would need to be in the package. If you need these shims, oyu will find them pretty much perfect for any standard doorbell swap out.
Finally, please don't poorly rate it of thou bought this for something other than RING Doorbell Pro. It's not designed for other units and they clearly state that.