add_filter('woocommerce_order_product_title', 'xa_product_dimension_add_func',99,2);

function xa_product_dimension_add_func($item_name ='', $product ='')
{
	if(!empty($product))
	{
		return $item_name . ' <small>( '.wc_format_dimensions($product->get_dimensions(false)).' )</small>';
	}else
	{
		return $item_name;
	}
}