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.

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

If you are looking to diversify your portfolio, consider Fidelity Advisor Technology M (FATEX Quick QuoteFATEX - Free Report) . With a much more diversified approach, FATEX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector. This fund is a winner, boasting an expense ratio of 1.23%, management fee of 0.52%, and a five-year annualized return track record of 19.91%.

Goldman Sachs Flex Cap Growth A (GALLX Quick QuoteGALLX - Free Report) is a stand out amongst its peers. GALLX 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 12.25%, expense ratio of 0.96% and management fee of 0.55%, this diversified fund is an attractive buy with a strong history of performance.

VY T. Rowe Price Diversified Mid Cap Growth Investor (IAXIX Quick QuoteIAXIX - Free Report) : 0.78% expense ratio and 0.74% management fee. IAXIX is a Mid Cap Growth mutual fund. These funds aim to target companies with a market capitalization between $2 billion and $10 billion that are also expected to exhibit more extensive growth opportunities for investors than their peers. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 10.31% over the last five years.

There you have it. If your financial advisor had you put your money into any of our top-ranked funds, then they've got you covered. If not, you may need to talk.