The S&P 500 is at record highs, and there are valid reasons to be concerned that a decline may be coming.

Many top funds that are built around the index size their investments in its components based on the companies’ market caps.

Some S&P 500 ETFs, however, use different methods to weight their portfolios, which gives them different risk profiles.

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Investing in the S&P 500 has historically been a good strategy for investors. A simple buy-and-hold approach to the index can generate solid returns in the long run.

The index is composed of 500 of the largest public U.S. companies, which makes it broad and diversified. However, because it is market-cap weighted, its value is heavily concentrated in the largest of those companies. And because many exchange-traded funds (ETFs) that track it follow that same formula, they are too.

The list of such funds includes the popular SPDR S&P 500 ETF (NYSEMKT: SPY). Its top three holdings – Nvidia, Microsoft, and Apple – together account for around 22% of its portfolio. This level of concentration may be a problem for you as an investor, particularly if you’re concerned that megacap tech stocks may be overpriced and due for declines in the near future.

One way to reduce your risk from that possibility would be to look at ETFs that weight their holdings differently, giving you exposure to the index’s wide array of companies, but with a less lopsided balance. Two that you may want to consider today are the **Invesco S&P 500 Revenue ETF **(NYSEMKT: RWL) and the **Invesco S&P 500 Equal Weight ETF **(NYSEMKT: RSP).

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As its name suggests, this Invesco fund tracks the S&P 500, but weights its positions in stocks based on the companies’ revenues. It also has a maximum weight of 5% per stock, ensuring that no single holding accounts for an excessive slice of the portfolio.

Today, the top three holdings in the fund are Amazon, Walmart, and Apple. Those three combine to make up just over 10% of the ETF’s portfolio, making it an attractive alternative to the SPY ETF. The one downside is that the Invesco S&P 500 Revenue ETF has an expense ratio of 0.39%, higher than the SPY ETF’s expense ratio of just over 0.09%. Over time, the fees a fund charges investors can add up, sapping their returns. However, for risk-averse investors who are looking for a safer investment overall, the trade-off here may be well worth it.

This year, the SPDR S&P 500 ETF has risen by around 17% while the revenue-tilted Invesco fund has climbed by a more modest 14%. That may seem underwhelming, but the payoff for accepting those weaker results could come if we enter an off period for the market, potentially due to the inflated valuations of tech sector powerhouses.