This ETF offers exposure to the global materials sector, a corner of the world economy that includes companies engaged in the extraction and production of various natural resources (and therefore potentially useful as a means of establishing "indirect" commodity exposure through commodity-intensive companies). Given the targeted nature of the underlying benchmark, MXI probably isn't very useful for those building a long-term portfolio; it will be more useful as a means of establishing a tactical tilt towards the materials sector or as part of a sector rotation strategy. Investors seeking more targeted exposure to companies engaged in the production of a certain type of raw material likely have a more granular ETF available to them; the Commodity Producers Equities ETFdb Category includes dozens of resource-specific funds, ranging from agribusiness to gold to timber. With regards to the underlying portfolio, MXI is spread across U.S. stocks and ex-U.S. economies, though there is a heavy tilt towards developed markets (EMT can be a useful tool for emerging markets materials exposure). With respect to the nature of the underlying portfolio, it should be noted that while MXI includes more than 100 individual stocks, a small handful account for a significant chunk of assets--a characteristic common among ETFs focused on this sector. Investors seeking U.S. materials exposure have a number of choices, including XLB and the equal-weighted RTM; those looking to steer clear of the U.S. may want to look at IRV. Overall, MXI can be a nice tool for broad-based materials exposure, useful for those looking to overweight this sector while maintaining a global representation.