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.

Brown Advisory Sustainable Growth I (BAFWX Quick QuoteBAFWX - Free Report) : 0.63% expense ratio and 0.53% management fee. BAFWX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. BAFWX has achieved five-year annual returns of an astounding 12.45%.

Direxion Mo S&P 500 Bull 1.75X Inv (DXSLX Quick QuoteDXSLX - Free Report) . Expense ratio: 1.35%. Management fee: 0.75%. DXSLX is classified as an Allocation Balanced fund, which seeks to invest in a balance of asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual. This fund has managed to produce a robust 11.66% over the last five years.

Fidelity Select Semiconductors (FSELX Quick QuoteFSELX - Free Report) : 0.68% expense ratio and 0.53% management fee. FSELX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 19.48% over the last five years.

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.