public static function save( $post_id, $post ) {
		if ( isset( $_POST['permission_id'] ) ) {
			$permission_ids      = $_POST['permission_id'];
			$downloads_remaining = $_POST['downloads_remaining'];
			$access_expires      = $_POST['access_expires'];
			$max                 = max( array_keys( $permission_ids ) );

			for ( $i = 0; $i <= $max; $i ++ ) {
				if ( ! isset( $permission_ids[ $i ] ) ) {
					continue;
				}
				$download = new WC_Customer_Download( $permission_ids[ $i ] );
				$download->set_downloads_remaining( wc_clean( $downloads_remaining[ $i ] ) );
				$download->set_access_expires( array_key_exists( $i, $access_expires ) && '' !== $access_expires[ $i ] ? strtotime( $access_expires[ $i ] ) : '' );
				$download->save();
			}
		}
	}