NEW YORK ( TheStreet) - New exchange traded funds often seek to target investment trends. One of the hottest areas in recent years has been the materials sector.U.S.-based investors know more about commodities than they did 10 years ago and just about every ETF provider have introduced funds that invest in commodity stocks or the materials themselves. Two new funds were introduced a few days ago: the First Trust ISE Global Copper Index Fund ( CU) and the First Trust ISE Global Platinum Index Fund ( PLTM). Most of the existing materials funds are broad, with exposure to large miners such as Vale ( VALE) and big agribusiness companies like Monsanto ( MON). Van Eck also offers the Market Vector Gold Miners ETF (GDX) and the Market Vectors Junior Gold Miners ETF ( GDXJ). The two First Trust ETFs are the first to specialize in metals other than gold. The trouble with focused funds is that it can be tough to find enough stocks to fill them. That appears to be the case with the Global Copper Index Fund. BHP Billiton ( BHP) is the largest holding in the copper ETF but copper production at BHP is dwarfed by its production in coal and iron ore. Xstrata, the second-largest position, has five business segments and copper is just one. MMC Norilsk Nickel produces more nickel and palladium than copper. These companies mine a lot of copper, but the amount mined is not large relative to the size of the companies. The Global Copper ETF also includes companies like Freeport McMoRan Copper & Gold ( FCX) and Southern Copper ( PCU), which are purer plays. Given the heavy weightings of broad-line miners, it is possible that the Global Copper Index Fund will not capture a trend in which copper differentiates itself from other metals. The Global Platinum Index Fund is less likely to experience "style drift." The largest companies include Norilsk Nickel, Johnson Matthey and Eastern Platinum. Both funds are concentrated, with the copper fund having 27 holdings and the platinum fund having 25. Six stocks in the copper fund have weightings larger than 5% and the platinum fund has 10 stocks weighted at 5% or larger. Both funds are heavily weighted toward Canada. The platinum fund also has large exposures to South Africa and Australia. Between the two, the Global Platinum Index Fund offers more utility because it offers access to a space that wasn't previously accessible. Most of the large holdings in the copper fund feature prominently in other materials funds. However, the companies in the platinum fund are generally smaller. The platinum fund's median market cap is $775 million versus $2.6 billion for the copper fund, and it is likely you've never heard of most of the companies in the platinum fund.