metamask-extension/ui/app/css/fonts.css

@import url(https://fonts.googleapis.com/css?family=Roboto:300,500);
@import url(https://maxcdn.bootstrapcdn.com/font-awesome/4.4.0/css/font-awesome.min.css);

@font-face {
  font-family: 'Montserrat Regular';
    src: url('/fonts/Montserrat/Montserrat-Regular.woff') format('woff');
    src: url('/fonts/Montserrat/Montserrat-Regular.ttf') format('truetype');
  font-weight: normal;
  font-style: normal;
  font-size: 'small',

}

@font-face {
  font-family: 'Montserrat Bold';
    src: url('/fonts/Montserrat/Montserrat-Bold.woff') format('woff');
    src: url('/fonts/Montserrat/Montserrat-Bold.ttf') format('truetype');
  font-weight: normal;
  font-style: normal;
}