Investors are rushing to get out of a top exchange-traded note before it stops trading publicly, and those who fail to find a buyer may be stuck for years in a widely misunderstood product. Credit Suisse's $1.1 billion VelocityShares 3x Long Crude Oil ETN (UWTI) is poised on Dec. 8 to become the largest-ever note to be delisted from U.S. exchanges.

Investors hold $22 billion of U.S. ETNs which, like debt, constitute a pledge by an issuer. Payouts are based on the performance of the underlying asset, but the notes do not "hold" those assets, unlike ETFs to which they are often compared.

UWTI is widely used by mom-and-pop investors, many of whom are unaware of these differences and may find out too late, analysts said.

Banks, under regulatory pressure to cut risk since the financial crisis, have been issuing fewer ETNs and delisting existing ones to focus on their core businesses.

It is rare for a delisting to come without a new redemption option for investors who retain the product. Credit Suisse's move may make investors wary of ETNs.

"The benefits of ETNs, in most segments of the market, are not that great," said Michael Iachini, managing director of mutual fund and exchange traded fund (ETF) research at Charles Schwab Investment Advisory Inc. "It's not a great loss."

Upon delisting, ETF holders are typically paid out in cash, while ETN holders are at the mercy of the issuer.

After that, investors looking to sell would be forced to find a buyer "over-the-counter," where investors are not guaranteed anything close to what the notes are worth.

Several traders and analysts expect Credit Suisse to announce plans to effectively redeem the remaining notes for cash, but the bank has not said whether it would do so.

Over the last decade, 89 ETNs have closed out of a total of nearly 300 issued, according to fund researcher Morningstar Inc. The largest closure was in 2015, when Royal Bank of Scotland Plc ended its stock-tracking $478 million U.S. Large Cap Trendpilot ETN.

Investors pulled nearly $675 million from UWTI in the two weeks through Nov. 30, according to fund researcher Thomson Reuters Lipper. The march toward their delisting has occurred despite a massive run-up in oil prices, which has boosted the ETN's price.

Credit Suisse said in a Nov. 16 statement it would delist the ETN to better align "its product suite with its broader strategic growth plans."

Investors hold UWTI for six days on average, according to Deutsche Bank Securities Inc. Those who do not sell UWTI during the week of Dec. 5 could be forced to hold the notes for years since they do not officially expire until February 2032.

Credit Suisse, which in 2014 said it would wind down its commodities trading, declined to comment on plans for the ETN.

VelocityShares, a Janus Capital Group Inc. unit that provides services for the notes, also declined to comment.

Investors can book huge profits during oil price volatility, such as when OPEC agreed during the week of Nov. 28 to curb crude production in a bid to support prices.

Prices soared. UWTI, which promises to multiply the return of an oil futures index by three, leaped 25% on Nov. 30 alone.

A smaller related ETN, the $222 million VelocityShares 3x Inverse Crude Oil ETN, is also delisting Dec. 8. The notes actually attracted $60.2 million in the latest week, Lipper said.

Yet "leveraged" ETNs' volatile results have led to disappointments. Brokers have been sanctioned for selling the products to retail investors for whom they were not suitable.

Credit Suisse was sued by investors who owned a leveraged ETN after new issuances of the notes were suspended. A federal appeals court in 2014 ruled in favor of Credit Suisse, saying no reasonable investor could have read its disclosures without understanding the notes' risk.

Institutions account for only 16% of the funds' owners, according to a Deutsche Bank analysis. TD Ameritrade Inc., a retail-focused broker, said UWTI was among the most popular securities traded by millennials last year.

Issuers are not always willing to help after a fund is delisted, said Mariana Bush, head of closed-end fund and exchange-traded product research at Wells Fargo Advisors, who has helped financial advisers at the bank liquidate positions in delisted ETNs.

"It was a nightmare," she said. "Investors should be aware of it and should try to think about an exit strategy."