IEZ strays far from the neutral exposure of the oil & gas drilling & exploration market, instead opting for a narrower approach to the oil segment. The fund tracks a Dow Jones index that all but ignores the oil and gas transportation industry, but digs deep into the suppliers of equipment and services to oil fields and offshore platforms, such as drilling, exploration, seismic-information services and platform construction. It's also a fairly concentrated fund, with its top holdings comprising the majority of IEZ's total portfolio. IEZ selects and weights its constituents by market cap, with a cap of 22.5% per stock, while the aggregate weight of companies with greater than 4.5% are capped at 45% of the funds value. The index is rebalanced quarterly.