public function invocation( $sku, $not_used_1, $not_used_2, $text_font, $text_size ) {

		$ps[] = "50 50 moveto ({$sku}) (includetext textfont={$text_font} textsize={$text_size} height=0.5)";
		$ps[] = '/code128 /uk.co.terryburton.bwipp findresource exec';

		return implode( "\n", $ps ) . "\n";
	}