SCUBA Diving Rear-View Mirror

This is a head mounted rear-view mirror for SCUBA diving.

It can be used:
- to self check for bubbles (especially for solo divers using a backmount configuration)
- maybe look for buddies that like to stay behind :D

The mirror used is a 51mm (in diameter) blind spot / dead-angle mirror for cars that I've found on amazon for 5.89€ / 2 pcs:
- https://www.amazon.co.uk/gp/product/B01MYO60PU
- https://www.amazon.de/Verstellbare-Weitwinkel-Spiegel-Randlos-R%C3%BCckspiegel/dp/B0791BXT4M
- https://www.amazon.co.uk/Verstellbare-Weitwinkel-Spiegel-Randlos-R%C3%BCckspiegel/dp/B0791BXT4M
- https://www.amazon.it/Verstellbare-Weitwinkel-Spiegel-Randlos-R%C3%BCckspiegel/dp/B0791BXT4M
- https://www.amazon.fr/Verstellbare-Weitwinkel-Spiegel-Randlos-R%C3%BCckspiegel/dp/B0791BXT4M

(Different brands of the same Chinese mirror, just check that it's 51mm or 5.08cm).

The mirror comes with a 3M layer on the back. Otherwise some glue would suffice. The curvature of the mirror should be aroun