change the font size in the headline of related post

Hi,

how can i change the size of headline of related post? In which point should i put font size code?

function jetpackme_related_posts_headline( $headline ) {
$headline = sprintf(
‘<h3 class=”jp-relatedposts-headline”>%s</h3>’,
esc_html( ‘Check These Out!’ )
);
return $headline;
}
add_filter( ‘jetpack_relatedposts_filter_headline’, ‘jetpackme_related_posts_headline’ );

best regards, PAwel