EXHIBIT 10.6



                       NEXAR TECHNOLOGIES, INC. LETTERHEAD


December 17, 1996


Mr. William E. Johnson
Government Technology Services, Inc.
4100 Lafayette Center Drive
Chantilly, Virginia 22021-0808

                  Re:      Agreement Regarding Exclusivity
                           -------------------------------
Dear Mr. Johnson:

         This letter is to confirm the  agreement  between  Nexar  Technologies,
Inc. ("NEXAR") and Government Technology Services, Inc. ("GTSI") with respect to
GTSI's  exclusive  GSA  Schedule  B/C Letter of Supply  during the  1997/98  B/C
calendar year.  Pursuant to this agreement,  NEXAR has  communicated  its desire
that GTSI purchase at least  $35,000,000  worth of product during  calendar year
1997,  and the essential  spirit of the agreement is that GTSI would receive GSA
exclusivity  from NEXAR in exchange for  $35,000,000 in net sales.  If GTSI does
not achieve the following  quarterly  purchase  objectives  for two  consecutive
quarters, NEXAR reserves the right to withdraw GTSI's GSA exclusivity.

                  Q1                                          $ 4,900,000
                  Q2                                          $ 5,500,000
                  Q3                                          $12,700,000
                  Q4                                          $11,900,000
                                                              -----------
                  Total                                       $35,000,000

         Please sign below in acknowledgement of the above  understanding of the
agreement.

                                                  Very truly yours,


                                                 /s/Anthony Colangelo
                                                 --------------------------
                                                  Anthony Colangelo


GOVERNMENT TECHNOLOGY SERVICES, INC.


/s/ William E. Johnson
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