Custom font size for Text in SwiftUI

Question

I have a label in my view that I want to use the system font size in medium, with a size of 21 points.
I created a custom extension to re-use the font created:

extension Font {     static var primaryButton: Font {         return Font.custom("SFUIDisplay-Light", size: 21)     } } 

However, this does not have any effect. I changed the string to HelveticaNeue-UltraLight and it did work, so I'm guessing that SFUIDisplay-Light is simply the incorrect font name.
In font book, it says SFProText-Light, but that also did not work for me.

What is the correct font name of the San Francisco font in SwiftUI?
Or: how can I set the font size using the system font?

Answer 1

You can set an explicit size for the system font with:

.font(.system(size: 60)) 

Answer 2

You can set custom font size like this,

.font(.custom("FONT_NAME", size: 20))