Master limited partnership ETFs have attracted a lot of attention lately with investors on the lookout for income and non-correlated alternative investments for diversification.

Now, the largest exchange traded product for MLPs, JPMorgan Alerian MLP Index ETN (NYSEArca: AMJ), has placed a cap on its size. The move means the $4.3 billion exchange traded note could begin trading at a premium to net asset value if demand for the ETN remains strong.

ETF shares tend to trade in line with the value of the underlying securities. However, premiums and discounts can develop in exchange traded products when sponsors halt the creation of new shares. This causes the so-called arbitrage mechanism to break down. [Cap in Master Limited Partnership ETN May Trigger Premium]

For MLP investors, exchange traded products for this asset class include Alerian MLP ETF (NYSEArca: AMLP), Yorkville High Income MLP (NYSEArca: YMLP), Global X MLP (NYSEArca: MLPA) and UBS E-TRACS Alerian MLP Infrastructure ETN (NYSEArca: MLPI).

After AMJ, the next-largest offering for the sector is AMLP, which holds $3.3 billion in assets.

“Investors purchasing this ETF receive exposure to publicly traded partnership units called master limited partnerships whose business operations are concentrated in the transportation of petroleum liquids, such as gasoline and oil, and natural gas,” said Morningstar analyst Abraham Bailin in a report on AMLP.