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

Lord Abbett Growth Leaders R2 (LGLQX Quick QuoteLGLQX - Free Report) has a 1.26% expense ratio and 0.51% management fee. LGLQX 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 11.01% over the last five years, this fund clearly wins.

ProFunds Semicond UltraSector Investor (SMPIX Quick QuoteSMPIX - Free Report) . Expense ratio: 1.49%. Management fee: 0.75%. SMPIX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. This fund has managed to produce a robust 16.94% over the last five years.

ProFunds Semicond UltraSector Investor (SMPIX Quick QuoteSMPIX - Free Report) . Expense ratio: 1.49%. Management fee: 0.75%. Five year annual return: 16.94%. SMPIX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach.

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.