REPORT OF INDEPENDENT REGISTERED PUBLIC
ACCOUNTING FIRM

To the Shareholders of BlackRock GA Disciplined
Volatility Equity Fund and BlackRock GA Dynamic Equity
Fund and Board of Trustees of Managed Account Series:

In planning and performing our audits of the financial
statements of BlackRock GA Disciplined Volatility Equity
Fund and BlackRock GA Dynamic Equity Fund (formerly,
BlackRock GA Enhanced Equity Fund) of Managed Account
Series (the "Funds"), as of and for the year ended October 31,
2019, in accordance with the standards of the Public Company
Accounting Oversight Board (United States) (PCAOB), we
considered the Funds' internal control over financial reporting,
including controls over safeguarding securities, as a basis for
designing our auditing procedures for the purpose of expressing
our opinion on the financial statements and to comply with the
requirements of Form N-CEN, but not for the purpose of
expressing an opinion on the effectiveness of the Funds'
internal control over financial reporting. Accordingly, we
express no such opinion.

The management of the Funds is responsible for establishing
and maintaining effective internal control over financial
reporting. In fulfilling this responsibility, estimates and
judgments by management are required to assess the expected
benefits and related costs of controls. A company's internal
control over financial reporting is a process designed to provide
reasonable assurance regarding the reliability of financial
reporting and the preparation of financial statements for
external purposes in accordance with generally accepted
accounting principles. A company's internal control over
financial reporting includes those policies and procedures that
(1) pertain to the maintenance of records that, in reasonable
detail, accurately and fairly reflect the transactions and
dispositions of the assets of the company; (2) provide
reasonable assurance that transactions are recorded as necessary
to permit preparation of financial statements in accordance with
generally accepted accounting principles, and that receipts and
expenditures of the company are being made only in
accordance with authorizations of management and directors of
the company; and (3) provide reasonable assurance regarding
prevention or timely detection of unauthorized acquisition, use,
or disposition of a company's assets that could have a material
effect on the financial statements.

Because of its inherent limitations, internal control over
financial reporting may not prevent or detect misstatements.
Also, projections of any evaluation of effectiveness to future
periods are subject to the risk that controls may become
inadequate because of changes in conditions or that the degree
of compliance with the policies or procedures may deteriorate.

A deficiency in internal control over financial reporting exists
when the design or operation of a control does not allow
management or employees, in the normal course of performing
their assigned functions, to prevent or detect misstatements on a
timely basis. A material weakness is a deficiency, or a
combination of deficiencies, in internal control over financial
reporting, such that there is a reasonable possibility that a
material misstatement of the company's annual or interim
financial statements will not be prevented or detected on a
timely basis.

Our consideration of the Funds' internal control over financial
reporting was for the limited purpose described in the first
paragraph and would not necessarily disclose all deficiencies in
internal control that might be material weaknesses under
standards established by the PCAOB. However, we noted no
deficiencies in the Funds' internal control over financial
reporting and its operation, including controls for safeguarding
securities, that we consider to be a material weakness, as
defined above, as of October 31, 2019.

This report is intended solely for the information and use of
management and the Board of Trustees of the Funds and the
Securities and Exchange Commission and is not intended to be
and should not be used by anyone other than these specified
parties.

/s/ Deloitte & Touche LLP
Boston, Massachusetts
December 20, 2019