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                    [LETTERHEAD OF SAGE LABORATORIES, INC.)

                                  May 19, 1998

To Our Stockholders:

      We are pleased to report that Sage Laboratories, Inc. (the "Company") has
entered into a merger agreement with Filtronic plc ("Filtronic") and one of its
subsidiaries that provides for the acquisition of the Company by Filtronic at a
price of $17.50 per share in cash. Under the terms of the proposed transaction,
a Filtronic subsidiary is today commencing a cash tender offer for all
outstanding shares of the Company's common stock at $17.50 per share. Following
the successful completion of the tender offer, the Filtronic subsidiary will be
merged into the Company and all shares not purchased by the Filtronic subsidiary
in the tender offer will be converted into the right to receive $17.50 per share
in cash in the merger.

      YOUR BOARD OF DIRECTORS HAS UNANIMOUSLY APPROVED THE FILTRONIC TENDER
OFFER AND DETERMINED THAT THE TERMS OF THE TENDER OFFER AND THE MERGER, TAKEN
TOGETHER, ARE FAIR TO, AND IN THE BEST INTERESTS OF, THE COMPANY AND ITS
STOCKHOLDERS. ACCORDINGLY, THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS
ACCEPTANCE OF THE FILTRONIC TENDER OFFER AND APPROVAL AND ADOPTION OF THE MERGER
AGREEMENT BY THE STOCKHOLDERS OF THE COMPANY.

      In arriving at its recommendations, the Board of Directors gave careful
consideration to a number of factors. These factors included the opinion dated
May 13, 1998, of KPMG Inc. ("KPMG"), financial advisor to the Company, to the
effect that, as of such date and based upon and subject to certain matters
stated in such opinion, the cash consideration of $17.50 per share to be
received by the public stockholders of the Company in the offer and the merger
was fair from a financial point of view to such public stockholders.

      Accompanying this letter is a copy of the Company's
Solicitation/Recommendation Statement on Schedule 14D-9. Also enclosed is
Filtronic's Offer to Purchase and related materials, including a Letter of
Transmittal for use in tendering shares. We urge you to read carefully the
enclosed materials, including KPMG's opinion, which is attached to the Schedule
14D-9.

      The management and directors of Sage Laboratories, Inc. thank you for the
support you have given the Company over the years.

                                          Sincerely,

                                          /s/ Carl A. Marguerite
                                          Carl A. Marguerite
                                          Chairman of the Board
                                          and Chief Executive Officer