The iPath family of exchange-traded notes (ETNs) literally doubled overnight. Barclays Bank is launching eight new ETNs today on the NYSE Arca exchange; the family already included eight ETNs.

The new ETNs are linked to eight subindexes of the Dow Jones-AIG Commodity Index, covering the Agriculture, Copper, Grains, Energy, Industrial, Livestock, Natural Gas and Nickel markets.

The bulk ($2.3 billion) of the existing iPaths' approximately $3.6 billion in total assets are located in the iPath Dow Jones-AIG Commodity Index Total Return ETN (NYSE: DJP), so BGI's decision to offer investors more granularity in their investment choices in that area makes sense. It already offers ETNs covering the S&P/Goldman Sachs Commodity Index (NYSE: GSP) and its crude oil subindex (NYSE: OIL).

The notes each carry an annual investor fee of 0.75% and have a 30-year maturity.

The new iPath ETNs aren't the only subindex commodity ETNs on the market today. The ELEMENTS ETN platform offers four products. The ELEMENTS Rogers International Commodity Total Return Index ETN (AMEX: RJI) tracks a broad commodity index, but the other three ETNs track subindexes of that index: Agriculture (AMEX: RJA), Energy (AMEX: RJN) and Metals (AMEX: RJZ). They represent the only competitors to the iPath commodities ETNs and also have expense ratios of 0.75%. Swedish Export Credit Corp. is the issuer.

Mainly, the ELEMENTS ETNs suffer from a lack of investor recognition. Barclays Bank's iPaths can piggyback on the success and established brand name of the Barclays Global Investors iShares exchange-traded funds. However, the ELEMENTS platform is starting from square one in a fairly new and unknown product area and does not have that cross-marketing advantage.

What it does have going for it is Jim Rogers' celebrity, which is not inconsequential. Also, the Rogers indexes are among the most thorough commodity indexes available, which could appeal to investors looking for diversified exposure.