Exhibit 4.5


                                     [Form of Capital Securities Certificate]

         THE CAPITAL SECURITIES  EVIDENCED HEREBY, ANY CONVERTIBLE  SUBORDINATED
DEFERRABLE  INTEREST  DEBENTURES ISSUABLE HEREWITH AND THE COMMON STOCK ISSUABLE
UPON THEIR CONVERSION HAVE NOT BEEN REGISTERED UNDER THE U.S.  SECURITIES ACT OF
1933 (THE "SECURITIES ACT") AND MAY NOT BE OFFERED,  SOLD,  PLEDGED OR OTHERWISE
TRANSFERRED EXCEPT IN WHOLE OR IN PART (BUT IF IN PART, IN AMOUNTS NOT LESS THAN
$10,000,000 IN PRINCIPAL AMOUNT) AND ONLY IN COMPLIANCE WITH THE REQUIREMENTS OF
THE SECURITIES ACT OR PURSUANT TO AN APPLICABLE EXEMPTION THEREFROM.

         NO EMPLOYEE  BENEFIT OR OTHER PLAN  SUBJECT TO TITLE I OF THE  EMPLOYEE
RETIREMENT INCOME SECURITY ACT OF 1974, AS AMENDED ("ERISA"), OR SECTION 4975 OF
THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE") (EACH, A "PLAN"),  NO
ENTITY WHOSE  UNDERLYING  ASSETS  INCLUDE  "PLAN ASSETS" BY REASON OF ANY PLAN'S
INVESTMENT IN THE ENTITY (A "PLAN ASSET ENTITY"),  AND NO PERSON INVESTING "PLAN
ASSETS" OF ANY PLAN, MAY ACQUIRE OR HOLD THIS CAPITAL SECURITIES  CERTIFICATE OR
ANY  INTEREST  HEREIN,  UNLESS  SUCH  PURCHASER  OR HOLDER IS  ELIGIBLE  FOR THE
EXEMPTIVE RELIEF AVAILABLE UNDER U.S. DEPARTMENT OF LABOR PROHIBITED TRANSACTION
CLASS  EXEMPTION  ("PTCE")  96-23,  95-60,  91-38,  90-1  OR  84-14  OR  ANOTHER
APPLICABLE  EXEMPTION  WITH RESPECT TO SUCH PURCHASE OR HOLDING AND, IN THE CASE
OF ANY  PURCHASER  OR HOLDER  RELYING ON ANY  EXEMPTION  OTHER THAN PTCE  96-23,
95-60,  91-38,  90-1 OR 84-14, HAS COMPLIED WITH ANY REQUEST BY THE DEPOSITOR OR
THE ISSUER TRUST FOR AN OPINION OF COUNSEL OR OTHER EVIDENCE WITH RESPECT TO THE
AVAILABILITY  OF SUCH  EXEMPTION.  ANY  PURCHASER  OR  HOLDER  OF  THIS  CAPITAL
SECURITIES CERTIFICATE OR ANY INTEREST HEREIN WILL BE DEEMED TO HAVE REPRESENTED
BY ITS  PURCHASE  AND HOLDING  HEREOF THAT IT EITHER (A) IS NOT A PLAN OR A PLAN
ASSET ENTITY AND IS NOT  PURCHASING  SUCH  SECURITIES ON BEHALF OF OR WITH "PLAN
ASSETS" OF ANY PLAN, OR (B) IS ELIGIBLE FOR THE EXEMPTIVE RELIEF AVAILABLE UNDER
PTCE 96-23,  95-60,  91-38, 90-1 OR 84-14 OR ANOTHER  APPLICABLE  EXEMPTION WITH
RESPECT TO SUCH PURCHASE OR HOLDING.






Certificate Number                              Aggregate Liquidation Amount

     P-___                                              $300,000,000


                    Certificate Evidencing Capital Securities

                                       of

                                 HSB Capital II

                         Convertible Capital Securities
                (liquidation amount $1,000 per Capital Security)


     HSB Capital II, a statutory  business  trust  created under the laws of the
State of Delaware (the "Issuer  Trust"),  hereby certifies that [Name of Holder]
(the  "Holder") is the  registered  owner of Three  Hundred  Thousand  (300,000)
capital securities  (aggregate  Liquidation Amount Three Hundred Million dollars
($300,000,000))  of  the  Issuer  Trust   representing  a  preferred   undivided
beneficial  interest  in the  assets  of the  Issuer  Trust and  designated  the
Convertible Capital Securities  (liquidation amount $1,000 per Capital Security)
(the "Capital Securities"). The Capital Securities are transferable on the books
and records of the Issuer  Trust,  in person or by a duly  authorized  attorney,
upon surrender of this certificate duly endorsed and in proper form for transfer
as provided  in Section  5.4 of the Trust  Agreement  (as  defined  below).  The
designations, rights, privileges, restrictions,  preferences and other terms and
provisions of the Capital  Securities are set forth in, and this certificate and
the Capital  Securities  represented hereby are issued and shall in all respects
be subject to the terms and  provisions  of, the Trust  Agreement  of the Issuer
Trust,  dated as of December 31,  1997,  as the same may be amended from time to
time (the "Trust Agreement"),  among HSB Group, Inc., a Delaware corporation, as
Depositor,  The First  National  Bank of  Chicago,  as Property  Trustee,  First
Chicago Delaware,  Inc., as Delaware Trustee,  and the  Administrative  Trustees
named therein,  including the designation of the terms of the Capital Securities
as set forth  therein.  The Holder is entitled to the benefits of the  Guarantee
Agreement,  dated as of December 31, 1997 (the "Guarantee  Agreement"),  entered
into by HSB Group,  Inc. and The First  National  Bank of Chicago,  as guarantee
trustee, to the extent provided therein. The Issuer Trust will furnish a copy of
the Trust  Agreement and the Guarantee  Agreement to the Holder  without  charge
upon written  request to the Issuer Trust at its principal  place of business or
registered office.

     Upon  receipt  of this  certificate,  the  Holder  is  bound  by the  Trust
Agreement and is entitled to the benefits thereunder.




                                                       





     IN WITNESS WHEREOF, one of the Administrative  Trustees of the Issuer Trust
has executed this certificate this 31st day of December, 1997.

                                       HSB CAPITAL II


                                       By:
                                       Name:
                                       Administrative Trustee






         TRUSTEE'S CERTIFICATE OF AUTHENTICATION:

         This is one of the Securities referred to in the
         within-mentioned Trust Agreement


         THE FIRST NATIONAL BANK OF CHICAGO, as Property Trustee


         By:
               Name:
               Title:



                                                       





                                  ASSIGNMENT

         FOR VALUE RECEIVED,  the undersigned assigns and transfers this Capital
Security to:

     -------------------------------------------------------------

    (Insert assignee's social security or tax identification number)

    --------------------------------------------------------------

                (Insert address and zip code of assignee)


and irrevocably appoints
- --------------------------------------------------------------------------

agent to transfer this Capital Securities Certificate on the books of the Issuer
Trust. The agent may substitute another to act for him or her.

Date: ________________

Signature:________________________________________________________
(Sign exactly as your name appears on the other side of this Capital
 Security Certificate)

The  signature(s)  should be  guaranteed  by an eligible  guarantor  institution
(banks,  stockbrokers,  savings  and loan  associations  and credit  unions with
membership in an approved signature guarantee  medallion  program),  pursuant to
S.E.C. Rule 17Ad-15.