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.

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

Victory Sycamore Established Value R (GETGX Quick QuoteGETGX - Free Report) : 1.1% expense ratio and 0.45% management fee. GETGX is a Mid Cap Value mutual funds that aims to target medium-sized companies that possess strong value and income opportunities for investors. With annual returns of 10.07% over the last five years, this fund is a winner.

JPMorgan Mid Cap Growth Fund R5 (JMGFX Quick QuoteJMGFX - Free Report) . Expense ratio: 0.79%. Management fee: 0.65%. JMGFX is a Mid Cap Growth mutual fund. These mutual funds choose companies with a stock market valuation between $2 billion and $10 billion. This fund has managed to produce a robust 10.66% over the last five years.

ProFunds UltraBull Fund Investor (ULPIX Quick QuoteULPIX - Free Report) . Expense ratio: 1.46%. Management fee: 0.75%. Five year annual return: 13.11%. ULPIX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset.

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.