Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

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

Fuller & Thayler Behavioral Small Cap R6

(FTHFX Quick QuoteFTHFX - Free Report) has a 0.63% expense ratio and 0.6% management fee. FTHFX is a Small Cap Blend mutual fund, and usually targets stocks with market caps of less than $2 billion, letting investors diversify their funds among other kinds of small-cap equities. With yearly returns of 16.15% over the last five years, this fund clearly wins.

JPMorgan Mid Cap Growth Fund R6

(JMGMX Quick QuoteJMGMX - Free Report) is a stand out amongst its peers. JMGMX is a Mid Cap Growth mutual fund. Mid Cap Growth funds pick stocks--usually companies with a market cap between $2 billion and $10 billion--that demonstrate extensive growth opportunities for investors compared to their peers. With five-year annualized performance of 12.35%, expense ratio of 0.7% and management fee of 0.65%, this diversified fund is an attractive buy with a strong history of performance.

Transamerica Large Value Opps R4

(TLOFX Quick QuoteTLOFX - Free Report) : 0.75% expense ratio and 0.45% management fee. TLOFX is a Large Cap Value fund. These funds invest in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. With a five-year annual return of 11.12%, this fund is a well-diversified fund with a long track record of success.

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.