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.

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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

AB Large Cap Growth K (ALCKX Quick QuoteALCKX - Free Report) has a 0.94% expense ratio and 0.48% management fee. ALCKX 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 yearly returns of 10.68% over the last five years, this fund clearly wins.

Fidelity Select Tech Hardware (FDCPX Quick QuoteFDCPX - Free Report) is a stand out amongst its peers. FDCPX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. With five-year annualized performance of 11.17%, expense ratio of 0.72% and management fee of 0.53%, this diversified fund is an attractive buy with a strong history of performance.

Neuberger Berman Guardian Trust (NBGTX Quick QuoteNBGTX - Free Report) . Expense ratio: 1.03%. Management fee: 0.88%. Five year annual return: 10.33%. NBGTX is a part of the Large Cap Value category, and invests in equities with a market capitalization of $10 billion or more, but whose share prices do not reflect their intrinsic value.

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.