If you want to make your set up a right angle (90 Degree) then you need to measure the angle of your downstem.
If your downstem has a 45 Degree angle then you would want a 45 Degree Angle Adapter to make a 90 Degree Right Angle.
If your downstem has a 45 Degree angle then you would want a 45 Degree Angle Adapter to make a 90 Degree Right Angle.