@font-face not working in polymer/web-components

I'm trying to get a web font into my polymer component, however the font is failing to render. Could someone shed some light on this? Google hasn't been giving me much love on this issue. If you need any more info then just let me know. Thanks!

@font-face {
font-family: 'open_sansextrabold';
src: url('fonts/OpenSans-ExtraBold-webfont.eot');
src: url('fonts/OpenSans-ExtraBold-webfont.eot?#iefix') format('embedded-opentype'),
     url('fonts/OpenSans-ExtraBold-webfont.woff') format('woff'),
     url('fonts/OpenSans-ExtraBold-webfont.ttf') format('truetype'),
     url('fonts/OpenSans-ExtraBold-webfont.svg#open_sansextrabold') format('svg');
font-weight: normal;
font-style: normal;
}

header a {
font-family: "open_sansextrabold";
display: block;
height: 50px;
width: 150px;
color: #fff;
text-decoration: none;
text-align: center;
line-height: 50px;
transition: background-color 1s ease;
-webkit-transition: all 140ms cubic-bezier(0.420, 0.000, 0.580, 1.000); 
-moz-transition: all 140ms cubic-bezier(0.420, 0.000, 0.580, 1.000); 
 -o-transition: all 140ms cubic-bezier(0.420, 0.000, 0.580, 1.000); 
    transition: all 140ms cubic-bezier(0.420, 0.000, 0.580, 1.000); /* ease-in-out */

-webkit-transition-timing-function: cubic-bezier(0.420, 0.000, 0.580, 1.000); 
-moz-transition-timing-function: cubic-bezier(0.420, 0.000, 0.580, 1.000); 
 -o-transition-timing-function: cubic-bezier(0.420, 0.000, 0.580, 1.000); 
    transition-timing-function: cubic-bezier(0.420, 0.000, 0.580, 1.000); /* ease-in-out */
}