Legendary investor Warren Buffett believes that the most critical factor in picking a successful investment is determining the durability of a company's competitive advantage or "moat." An economic moat refers to a company's ability to maintain a competitive advantage over its competitors to protect its profits and market share.

A company can create a moat through cost advantages, having a size advantage, ensuring high switching costs and possessing unique intangibles, such as patents and brand recognition. For example, Apple Inc. (NASDAQ: AAPL) has created an economic moat through its perceived quality and brand recognition that has allowed the company to protect market share from competitors offering lower-priced products. (See also: How Does Warren Buffett Choose His Stocks?)

Investors who want to embrace the central pillar of Buffett's investment strategy should consider these three exchange-traded products (ETPs) that provide exposure to companies that have sustainable economic moats. (See also: The Advantages of Wide Moats.)

VanEck Vectors Morningstar Wide Moat ETF (NYSEARCA: MOAT)

The VanEck Vectors Morningstar Wide Moat ETF, formed in 2012, aims to provide similar returns to the Morningstar Wide Moat Focus Index. The fund does this by investing a minimum of 80% of its assets in securities that make up the underlying index. These securities are companies that Morningstar Inc. deems to have a substantial competitive advantage gained from proprietary operations and assets, such as patents and high switching costs. Key stocks in the ETF's portfolio include Twenty-First Century Fox, Inc. Class A (NASDAQ: FOXA), Campbell Soup Company (NYSE: CPB), Amazon.com, Inc. (NASDAQ: AMZN) and Dominion Energy, Inc. (NYSE: D). In total, the fund's basket holds 49 stocks. (See also: Amazon: 10 Secret’s You Didn't Know.)

The VanEck Vectors Morningstar Wide Moat ETF has assets under management (AUM) of $3.4 billion as of October 2020. Its expense ratio of 0.48% is higher than the 0.33% category average. As of October 2020, the fund has five- and three-year annualized returns of 15.97% and 14.34%, respectively. Year to date (YTD), MOAT has returned 3.57%.

VanEck Vectors Morningstar International Moat ETF (NYSEARCA: MOTI)

Launched in 2015, the VanEck Vectors Morningstar International Moat ETF seeks to track the performance of the Morningstar Global ex-US Moat Focus Index. The manager achieves this by investing the majority of the fund's assets in securities that comprise the benchmark index. These are primarily international companies that Morningstar believes to have a competitive advantage and attractive valuation. The ETF's top three holdings of Kion Group AG (KGX.DE), Elekta AB (EKTAB SS), and NIDEC CORP (6594 JP) carry a cumulative weighting of 8.29%.

The VanEck Vectors Morningstar International Moat ETF has net assets of $51.4 million and charges investors an annual management fee of 0.56%. Although the fund has a disappointing YTD return of -5.22%, it returned 6.50% over the past 12 months as of October 2020. (For more, see: The 5 Best Dividend-Paying ETFs.)

Elements Morningstar Wide Moat Focus Total Return Index ETN (NYSEARCA: WMW)

Created in 2007, the Elements Morningstar Wide Moat Focus Total Return Index ETN attempts to replicate the returns of the Morningstar Wide Moat Focus Index. It does this by investing in securities that are constitutes of the tracked index. This includes large-capitalization companies that can exploit their competitive advantage. Top allocations include Twenty-First Century Fox Inc. Class A at 2.92%, Eli Lilly and Company (NYSE: LLY) at 2.90% and Biogen Inc. (NASDAQ: BIIB) at 2.78%. The exchange-traded note (ETN) holds 46 securities in total. (See also: How 21st Century Fox Makes Its Money.)

The Elements Morningstar Wide Moat Focus Total Return Index ETN is much smaller than the first two funds, with just $19.87 million in AUM. It has a relatively high expense ratio of 0.75% but has rewarded investors with a strong performance over an extended period with a 10-year return of 13.47%, a five-year return of 12.54% and a three-year return of 14.7%. The ETN also has an impressive YTD return of 6.63%.