1. Where two or more insurers share the same risk. A co-insurer is not bound to follow the decision of another co-insurer, except where he has given authority for the other insurer to act on his behalf. Each co-insurance is a separate contract with the insured. 2. Where an insured shares a part of the risk, e.g. 10 per cent of each claim (co-insurance clause), the insured is said to be a co-insurer.