Fund managers in their attempt to attract risk averse investors by making offerings that include participation in the high return risky asset classes such as equities and commodities fall in this category. Such funds promise a minimum return such as a capital guarantee or return on a low risk investment, such as a deposit or bond.
These are simple to manufacture, but have some constraints. They come in one fixed size and fixed maturity issue. Unlike open-ended funds they cannot be redeemed at any time.