[Correction: This article originally listed the expense ratio for SNO as 0.47%. It is actually 0.51%.]

It seemed like the Northern Trust exchange-traded funds were in registration forever, but now a few of its "NETS" (Northern Trust Exchange-Traded Shares) have been debuting every week since the first batch was launched in April. Today three ETFs covering Belgium, the Netherlands and China listed on the NYSE Arca platform:

• NETS Hang Seng China Enterprises Index Fund (NYSE Arca: SNO)
• NETS BEL 20^® Index Fund (NYSE Arca: BRU)
• NETS AEX-Index Fund (NYSE Arca: AEX)

The NETS Hang Seng China Enterprises Index Fund (NYSE Arca: SNO) is perhaps the most interesting of the three. Its underlying index covers the "H" shares - which are basically shares in companies based in mainland China that have listed on the Hong Kong Stock Exchange. With China's stock markets largely closed to foreign investment, the H-shares are one of the few ways that foreign investors can gain direct access to China's red-hot economy (some Chinese companies list shares on other exchanges, such as the NYSE, as well). SNO charges an expense ratio of 0.51%.

There are a few other China funds available, with the iShares FTSE/Xinhua 25 Index Fund (NYSE Arca: FXI) probably the most popular, with about $7.8 billion in assets, and also the most directly comparable. Like SNO, FXI invests only in H shares, but it charges a fee of 0.74%.

The NETS BEL 20^® Index Fund (NYSE Arca: BRU) tracks Belgium's blue-chip index of the 20 largest stocks listed on the Euronext Brussels exchange. Its only competitor is the iShares MSCI Belgium Index Fund (NYSE Arca: EWK), which charges 0.51%; BRU charges 0.47%.

The third ETF in the latest batch of NETS is the NETS AEX-Index Fund (NYSE Arca: AEX), which covers Amsterdam's top 25 blue-chip stocks. It carries an expense ratio of 0.47%. The competing iShares MSCI Netherlands Index Fund (NYSE Arca: EWN) charges 0.51%.

Read the prospectus for the NETS here.