(The following story contains a clarfication on the ETN's price.)

UBS, the Switzerland-based bank known for its private client business, today rolled out a one-off ETN that serves up double exposure to the large-cap Russell 1000 growth index. Crucially, the product is not part of UBS’ Etracs lineup of ETNs.

The UBS AG FI Enhanced Big Cap Growth ETN (NYSEArca: FBG) appears to be a security created and brought to market to satisfy an internal request. In other words, it’s not a function of a broader UBS strategic initiative aimed at exploiting a particular niche of the exchange-traded product market.

That makes it a bit more like so-called structured products that are marketed internally by big wire houses to high-net-worth clients as opposed to the public. Still, the exchange-traded component leaves open the door to a broader secondary-market clientele should the new ETN gain traction.

It’s not clear from the ETN’s prospectus why a large-cap strategy would be the one to bring to market under such special circumstance. The ETN is designed to deliver the returns of the Russell 1000 Growth Total Return Index, minus expenses.

Whatever the immediate motivation for bringing “FBG” to market, larger companies are generally seen as more able to weather economic downturns and volatile markets such as the ones that have prevailed since Europe’s debt crisis took center stage in global markets.

While UBS officials declined to comment on the new security, it seems clear that the new ETN is distinct in a number of ways that aren’t likely to become widespread—even in the world of ETNs, which is known for its off-the-beaten-track exposure schemes and sometimes-complex fees.

As an example, the all-in price of the ETN, referred to in the prospectus as the “Index Adjustment Factor,” is three-month U.S. dollar Libor (London interbank offered rate) accrued on a daily basis plus 0.13 percent of whatever assets are under management. In a fact sheet on the ETN that UBS circulated today, it said Libor was 47 basis points as of June 7, meaning the annualized expense ration on that date was 60 basis points.

That price is calculated on the basis of the actual number of calendar days elapsed in each quarterly period, divided by 360 and compounded quarterly during the ETN’s term, the prospectus said. It is an all-in fee that includes the cost of leverage.

Also, while leveraged ETNs marketed by UBS under the Etracs brand generally rebalance monthly, the new one-off ETN will only rebalance if its value drops by at least 20 percent.

The ETN has a 10-year term and will mature on June 8, 2022, the prospectus said.