There are over 1,800 exchange-traded funds (ETFs) available to investors, and so much choice can lead to paralysis when it comes to choosing the right funds for your portfolio.

Leveraged exchange-traded funds comprise a small fraction of the available ETFs and with good reason: These are highly complex investment vehicles with a high-risk, high-cost structure suitable for experienced investors with a high risk tolerance.

Leveraged funds use debt to achieve returns typically two or three times the index they track. For example, a fund with a 2:1 ratio would match each dollar of investor capital with $1 of invested debt (via futures contracts, derivatives), which in theory would double the return, less any management fees and transaction costs. If the index achieves a 1% gain, a 2:1 leveraged fund would return 2%. Of course, the opposite is also true: a 1% loss becomes 2% in a leveraged ETF. (See also: Dissecting Leveraged ETF Returns.)

These funds are not generally considered long-term investment options. In fact, most investors limit their exposure to a leveraged fund for a single day or matter of days in order to capitalize on a positive run of the underlying index. It's important to note that these funds are rebalanced daily and as a result, performance numbers may not closely track long-term performance of the S&P 500.

If you are interested in exposure to a leveraged ETF, here are 4 leveraged S&P indexed funds that are outperforming their peers. (See also: Leveraged ETFs: Are They Right for You?)

All year-to-date returns are based on the period of January 1, 2017 through May 18, 2017. Funds were selected on a combination of performance and assets under management.

ProShares Ultra S&P 500 ETF (SSO)

  • Issuer: ProShares
  • Assets Under Management: $1.82 billion
  • YTD Performance: 12.07%
  • Expense Ratio: 0.89%

This leveraged fund seeks to double the return of the S&P 500 for a single day (from one NAV calculation to the next) using stocks and derivatives.

ProShares Ultra Pro S&P 500 ETF (UPRO)

  • Issuer: ProShares
  • Assets Under Management: $821.64 million
  • YTD Performance: 18.12%
  • Expense Ratio: 0.95%

This ProShares ETF is similar to its sister fund, (SSO), but aims for returns of 300% of the S&P 500 using swap contracts for leverage. Both funds are rebalanced daily so multiplied returns may not match exactly the returns of the underlying index over the long term.

Below is proof of the power of leverage. UPRO's total return since inception is 1,286%, significantly more than S&P 500 during the same period.

Direxion Daily S&P 500 Bull 3x Shares ETF (SPXL)

  • Issuer: Direxion Funds
  • Assets Under Management: $534.26 million
  • YTD Performance: 17.90%
  • Expense Ratio: 0.95%

Direxion offers two S&P 500 leveraged S&P ETFs that seek to produce three times the return of the index on a daily basis. Direxion also has a companion fund, the Bear 3x shares, which aims for returns of 300% of the inverse of the S&P.

Bonus: Bearish Leveraged S&P ETF

ProShares Ultra Short S&P 500 (SDS)

  • Issuer: ProShares
  • Assets Under Management: $1.44 billion
  • YTD Performance: -11.65%
  • Expense Ratio: 0.90%

If you’re feeling bearish this year despite all evidence to the contrary, this S&P indexed ETF seeks to return -200% of the index returns on a daily basis.

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