protected function createClass()
	{
		$cols = $this->numOfColumns;
		if ($cols === self::COLUMNS_NONE) {
			return 'col';
		} elseif ($cols === self::COLUMNS_AUTO) {
			return 'col-auto';
		} else {
			// number
			if ($this->row->gridBreakPoint != NULL) {
				return 'col-' . $this->row->gridBreakPoint . '-' . $this->numOfColumns;
			} else {
				return 'col-' . $this->numOfColumns;
			}
		}
	}