The Crusty is a modern motorcycle mirror with an exclusive design. It is homologated for the European market, so this is the perfect replacement for your original ones.
Your bike needs two mirrors, but when replacing a broken mirror with the Crusty, you can simply order it without checking for the orientation. The Crusty is fully reversible, meaning that it can be mounted left or right regardless. Just make sure the reflective side is facing the rear. For the right hand mirror on a Yamaha, you get a left hand thread adapter.
The standard thread size for mirrors is M10, and the Crusty isn't any different. So it should fit just about any motorcycle, unless it's a genuine old timer. In that case, check the thread.
This package contains one mirror. You can mount and use it left or right. But, if you want to replace both mirrors, you need to order a second one. You knew that, right?