def get_all_reserved_instances(self, reserved_instances_id=None,
                                   filters=None):
        """
        Describes Reserved Instance offerings that are available for purchase.

        :type reserved_instance_ids: list
        :param reserved_instance_ids: A list of the reserved instance ids that
                                      will be returned. If not provided, all
                                      reserved instances will be returned.

        :type filters: dict
        :param filters: Optional filters that can be used to limit
                        the results returned.  Filters are provided
                        in the form of a dictionary consisting of
                        filter names as the key and filter values
                        as the value.  The set of allowable filter
                        names/values is dependent on the request
                        being performed.  Check the EC2 API guide
                        for details.

        :rtype: list
        :return: A list of :class:`boto.ec2.reservedinstance.ReservedInstance`
        """
        params = {}
        if reserved_instances_id:
            self.build_list_params(params, reserved_instances_id,
                                   'ReservedInstancesId')
        if filters:
            self.build_filter_params(params, filters)
        return self.get_list('DescribeReservedInstances',
                             params, [('item', ReservedInstance)], verb='POST')