There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

The easiest, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

Let's take a look at some of our top-ranked mutual funds with the lowest fees.

MassMutual Select Small Cap Growth Equity Admiral

(MSGLX): 1.15% expense ratio and 0.8% management fee. MSGLX is one of many Small Cap Growth mutual funds; these funds tend to create their portfolios around stocks with market capitalization of less than $2 billion. MSGLX has achieved five-year annual returns of an astounding 11.11%.

Vanguard Equity Income Admiral

(VEIRX) is a stand out amongst its peers. VEIRX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. With five-year annualized performance of 11.71%, expense ratio of 0.18% and management fee of 0.17%, this diversified fund is an attractive buy with a strong history of performance.

Wells Fargo Special Mid Cap Value A

(WFPAX): 1.12% expense ratio and 0.66% management fee. WFPAX is a Mid Cap Value fund, which usually invests in companies with a stock market valuation between $2 billion and $10 billion. With a five-year annual return of 11.08%, this fund is a well-diversified fund with a long track record of success.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.

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