 // Display Fields
    add_action('woocommerce_product_options_inventory_product_data', 'woocommerce_product_custom_fields');
    // Save Fields
    add_action('woocommerce_process_product_meta', 'woocommerce_product_custom_fields_save');
    function woocommerce_product_custom_fields()
    {
        global $woocommerce, $post;
        echo '<div class="product_custom_field">';
        // EAN_1
        woocommerce_wp_text_input(
            array(
                'id' => '_ean_1',
                'placeholder' => '',
                'label' => __('EAN_1', 'woocommerce'),
                'desc_tip' => 'true'
            )
        );
        
        // EAN_2
        woocommerce_wp_text_input(
            array(
                'id' => '_ean_2',
                'placeholder' => '',
                'label' => __('EAN_2', 'woocommerce'),
                'desc_tip' => 'true'
            )
        );
        
        // UVP
        woocommerce_wp_text_input(
            array(
                'id' => '_uvp',
                'placeholder' => '',
                'label' => __('UVP', 'woocommerce'),
                'desc_tip' => 'true'
            )
        );
       
       
        echo '</div>';
    }
    
        function woocommerce_product_custom_fields_save($post_id)
    {
        // EAN_1
        $woocommerce_custom_product_text_field_ean_1 = $_POST['_ean_1'];
            update_post_meta($post_id, '_ean_1', esc_attr($woocommerce_custom_product_text_field_ean_1));
            
        // EAN_2
        $woocommerce_custom_product_text_field_ean_2 = $_POST['_ean_2'];
           update_post_meta($post_id, '_ean_2', esc_attr($woocommerce_custom_product_text_field_ean_2));
            
        // UVP
        $woocommerce_custom_product_text_field_uvp = $_POST['_uvp'];
            update_post_meta($post_id, '_uvp', esc_attr($woocommerce_custom_product_text_field_uvp));
    
    }