You’d need to ask the owner.The Sum Insured should represent the total replacement value of the kit AS NEW at today’s prices.  You should be provided with this figure from the person or company who owns the kit.  We strongly advise that you do not estimate this figure yourself as, if this is wrong, you could be liable for the shortfall in the event of a claim, rather than the owner of the kit who gave you the wrong figure!You could always send the hire company, or person you are hiring from, a copy of your quote to check that they are happy with the sum insured.