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 investors' portfolios.

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

Nuveen Small-Cap Value Opps I (NSCRX): 0.95% expense ratio and 0.81% management fee. NSCRX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. NSCRX has achieved five-year annual returns of an astounding 17.65%.

Federated Hermes MDT MktNeutral A (QAMNX): 1.26% expense ratio and 0.8% management fee. QAMNX is a Long Short - Equity mutual fund, which look at taking long positions in equities that are expected to appreciate and short positions in equities that are projected to decline, but overall, hope to minimize their market exposure. With yearly returns of 12.68% over the last five years, QAMNX is an effectively diversified fund with a long reputation of solidly positive performance.

Bridgeway Ultra Small Company Market Fund (BRSIX Quick QuoteBRSIX - Free Report) . Expense ratio: 0.75%. Management fee: 0.5%. Five year annual return: 12.89%. BRSIX 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.

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.