It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

How can you tell a good mutual fund from a bad one? It's pretty basic: if the fund is diversified, has low fees, and shows strong performance, it's a keeper. Of course, there's a wide range, but using the Zacks Mutual Fund Rank, we've found three mutual funds that would be great additions to any long-term retirement investors' portfolios.

Let's learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

Fidelity Advisor Convertible Security Institutional (FICVX) has a 0.77% expense ratio and 0.57% management fee. FICVX is categorized as a Convertible Bonds fund, and in the fixed income world, these funds are quite unique. These types of securities are a hybrid, meaning they have components of both fixed income and equity. With yearly returns of 11.44% over the last five years, this fund clearly wins.

MFS Growth Fund I (MFEIX) is a stand out amongst its peers. MFEIX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. With five-year annualized performance of 15.88%, expense ratio of 0.59% and management fee of 0.49%, this diversified fund is an attractive buy with a strong history of performance.

T. Rowe Price Capital Opportunity R (RRCOX): 1.08% expense ratio and 0.33% management fee. RRCOX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 14.91% over the last five years.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.

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