Some ETFs track broad, easy-to-understand indexes. For example, the SPDR S&P 500 (NYSEArca: SPY) tracks the S&P 500, an index that millions of investors are familiar with. Other ETFs feature more focused, niche strategies. In some cases, a unique spin on accessing mid- and large-cap U.S. stocks can garner big returns.

The PowerShares Buyback Achievers (NYSEArca: PKW) is a fine example of such an ETF. PKW tracks an index that is comprised of stocks that have repurchased at least 5% of their total shares outstanding over the past year and is weighted by market cap. That has helped the ETF deliver consistent out-performance of SPY over lengthy time frames. [Buyback ETF Outperforming The Market]

Another ETF that features a niche concept is the Guggenheim Spin-Off ETF (NYSEArca: CSD). A spin-off is any company resulting from either of the following events: a spin-off distribution of stock of a subsidiary company by its parent company to parent company’s shareholders or equity “carve-outs” or “partial initial public offerings” in which a parent company sells a percentage of the equity of a subsidiary to public shareholders. [Spin-Off ETF Making Gains]

While spin-offs are often performed under the guise of creating shareholder value for investors in the parent company, not every spin-off becomes a star stock. Fortunately, CSD has an excellent track record of topping the S&P 500. In the past year, CSD has outpaced SPY by 1,860 basis points. Over the past 24 months, the spin-off ETF is up 62.9% compared to 33.4% for SPY.

CSD, which tracks the Beacon Spin-off Index, has achieved that stunning level of alpha generation against the S&P 500 with just a small number of holdings. Three years ago, CSD had 40 holdings, but today that number is just 27. The reason for the small number of holdings is that the index does not immediately add new spin-offs.

“The universe of companies eligible for inclusion in the Index includes companies that have been spun-off within the past 30 months (but not more recently than six months prior to the applicable rebalancing date),” according to Guggenheim.