Notice of Guaranteed Delivery
                                  for Tender of
                      Global Capital Securities, Series A

                (Liquidation Amount $1,000 Per Capital Security)
           
                                       of

                                  HSB Capital I
                     Fully and Unconditionally Guaranteed by

                                 HSB Group, Inc.

               This Notice of Guaranteed Delivery, or one
          substantially equivalent to this form, must be used to
          accept the Exchange Offer (as defined below) if (i)
          certificates for the Issuer Trust's (as defined below)
          Global Floating Rate Capital Securities, Series A (the
          "Original Capital Securities") are not immediately
          available, (ii) Original Capital Securities, the Letter of
          Transmittal and all other required documents cannot be
          delivered to The First National Bank of Chicago (the
          "Exchange Agent") on or prior to the Expiration Date (as
          defined in the Prospectus referred to below) or (iii) the
          procedures for delivery by book-entry transfer cannot be
          completed on a timely basis. This Notice of Guaranteed
          Delivery may be delivered by hand, overnight courier or
          mail, or transmitted by facsimile transmission, to the
          Exchange Agent. See "The Exchange Offer-Procedures for
          Tendering Original Capital Securities" in the Prospectus. In
          addition, in order to utilize the guaranteed delivery
          procedure to tender Original Capital Securities pursuant to
          the Exchange Offer, a completed, signed and dated Letter of
          Transmittal relating to the Original Capital Securities (or
          facsimile thereof) must also be received by the Exchange
          Agent on or prior to the Expiration Date. Capitalized terms
          not defined herein have the meanings assigned to them in the
          Prospectus. 

                  The Exchange Agent For The Exchange Offer Is:
                       The First National Bank of Chicago

                                    By Mail:
                   (Registered or Certified Mail recommended)
                       The First National Bank of Chicago
                             c/o First Chicago Trust
                               Company of New York
                                 14 Wall Street
                               8th Floor, Window 2
                            New York, New York 10005
                            Facsimile Transmissions:
                          (Eligible Institutions Only)
                                 (212) 240-8938
           
                To Confirm by Telephone or for Information Call:
                                 (212) 240-8801
                         By Hand or Overnight Delivery:

                       The First National Bank of Chicago
                   c/o First Chicago Trust Company of New York
                                 14 Wall Street
                               8th Floor, Window 2
                            New York, New York 10005

               DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN
          ADDRESS OTHER THAN AS SET FORTH ABOVE OR TRANSMISSION OF
          THIS NOTICE OF GUARANTEED DELIVERY VIA FACSIMILE TO A NUMBER
          OTHER THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A VALID
          DELIVERY. 

               This Notice of Guaranteed Delivery is not to be used to
          guarantee signatures. If a signature on a Letter of
          Transmittal is required to be guaranteed by an "Eligible
          Institution" under the instructions thereto, such signature
          guarantee must appear in the applicable space provided in
          the signature box on the Letter of Transmittal. 



          Ladies and Gentlemen:

               The undersigned hereby tenders to HSB Capital I, a
          Delaware business trust (the "Issuer Trust") and to HSB
          Group, Inc., a Connecticut corporation (the "Company"), upon
          the terms and subject to the conditions set forth in the
          Prospectus dated _______, 1997 (as the same may be amended
          or supplemented from time to time, the "Prospectus"), and
          the related Letter of Transmittal (which together constitute
          the "Exchange Offer"), receipt of which is hereby
          acknowledged, the aggregate principal amount of Original
          Capital Securities set forth below pursuant to the
          guaranteed delivery procedures set forth in the Prospectus
          under the caption "The Exchange Offer-Procedures for
          Tendering Original Capital Securities." 
           
           
          Aggregate Liquidation Amount:

          Name(s) of Registered Holder(s): 

          Amount Tendered: $(1)
           
          Certificate No.(s) (if available): 
           
           
           
          (Total Liquidation Amount Represented by Original Capital Securities 
          Certificate(s) 
           
          $ 
           
          If Original Capital Securities will be tendered by
          book-entry transfer, provide the following information: 
           
          DTC Account Number: 
           
          Date: 

                                PLEASE SIGN HERE

          X 

          X 

          ---------------------
          (1)  Must be in denominations of a Liquidation Amount of
               $1,000 and any integral multiple thereof, and not
               less than $100,000 aggregate Liquidation Amount.

               All authority herein conferred or agreed to be
               conferred shall survive the death or incapacity of
               the undersigned and every obligation of the
               undersigned hereunder shall be binding upon the
               heirs, personal representatives, successors and
               assigns of the undersigned.


          Signature(s) of Owner(s)
          or Authorized Signatory
          Date:

                        Area Code and Telephone Number: 

          Must be signed by the holder(s) of the Original Capital
          Securities as their name(s) appear(s) on certificates for
          Original Capital Securities or on a security position
          listing, or by person(s) authorized to become registered
          holder(s) by endorsement and documents transmitted with this
          Notice of Guaranteed Delivery. If signature is by a trustee,
          executor, administrator, guardian, attorney-in-fact, officer
          or other person acting in a fiduciary or representative
          capacity, such person must set forth his or her full title
          below. Please print name(s) and address(es) 

          (Name(s): 

          Capacity: 

          Address(es): 

                                    GUARANTEE

                    (Not To Be Used For Signature Guarantee)

               The undersigned, a firm or other entity identified in
          Rule 17Ad-15 under the Securities Exchange Act of 1934, as
          amended, as an "eligible guarantor institution," including
          (as such terms are defined therein): (i) a bank; (ii) a
          broker, dealer, municipal securities broker, municipal
          securities dealer, government securities broker or
          government securities dealer; (iii) a credit union; (iv) a
          national securities exchange, registered securities
          association or clearing agency; or (v) a savings association
          that is a participant in a Securities Transfer Association
          recognized program (each of the foregoing being referred to
          as an "Eligible Institution"), hereby guarantees to deliver
          to the Exchange Agent, at one of its addresses set forth
          above, either the Original Capital Securities tendered
          hereby in proper form for transfer, or confirmation of the
          book-entry transfer of such Original Capital Securities to
          the Exchange Agent's account at The Depository Trust Company
          ("DTC"), pursuant to the procedures for book-entry transfer
          set forth in the Prospectus, in either case together with
          one or more properly completed and duly executed Letter(s)
          of Transmittal (or facsimile thereof) and any other required
          documents within three business days after the date of
          execution of this Notice of Guaranteed Delivery. 

               The undersigned acknowledges that it must deliver the
          Letter(s) of Transmittal and the Original Capital Securities
          tendered hereby to the Exchange Agent within the time period
          set forth above and that failure to do so could result in a
          financial loss to the undersigned.
                             (Please Type or Print)


          Name of Firm: 

          Address: 

          Zip Code:

          Area Code and Telephone No. :

          Authorized Signature:

          Title: 

          Dated: 

          NOTE:     DO NOT SEND CERTIFICATES FOR ORIGINAL CAPITAL
                    SECURITIES WITH THIS FORM.  CERTIFICATES FOR
                    ORIGINAL CAPITAL SECURITIES SHOULD ONLY BE SENT
                    WITH YOUR LETTER OF TRANSMITTAL.