MXI is a basic materials fund that captures the sector-by-sector space reasonably, and its chief departure from the benchmark is in its large-cap tilt and heavy exposure to some industry heavyweights. Like the space it's capturing, MXI is a bit top-heavy with big multinationals dominating its top holdings, so investors must be aware of the funds portfolio before investing. MXI only uses a sampling method, which means it will invest in a sample of securities that collectively have an investment profile similar to that of the underlying index. The index and fund are market-cap-weighted and are rebalanced quarterly.