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 investors' portfolios.

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

Invesco Technology Fund R5 (FTPIX Quick QuoteFTPIX - Free Report) : 0.72% expense ratio and 0.6% management fee. With a much more diversified approach, FTPIX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector. With annual returns of 13.66% over the last five years, this fund is a winner.

One Rock (ONERX). Expense ratio: 1.39%. Management fee: 1%. ONERX is a Mid Cap Growth mutual fund. Mid Cap Growth funds pick stocks--usually companies with a market cap between $2 billion and $10 billion--that demonstrate extensive growth opportunities for investors compared to their peers. This fund has managed to produce a robust 32.47% over the last five years.

Janus Henderson Research Institutional (JAGRX): 0.82% expense ratio and 0.56% management fee. JAGRX 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. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 12.78% over the last five years.

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.