If you're invested in any of the funds in our "Magnificent Retirement Mutual Funds" list, congratulations on owning some of the best managed and top-performing mutual funds. If you are lucky enough to discover our list of Top-Ranked Funds for the first time, it's never too late to start investing with the best, especially when it comes to your retirement.

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 our Zacks 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.

T. Rowe Price Capital Opportunity R (RRCOX - Free Report) : 1.28% expense ratio and 0.49% management fee. RRCOX 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. RRCOX has achieved five-year annual returns of an astounding 10.56%.

JPMorgan Large Cap Growth R5 (JLGRX - Free Report) is a stand out amongst its peers. JLGRX 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 five-year annualized performance of 13.19%, expense ratio of 0.53% and management fee of 0.45%, this diversified fund is an attractive buy with a strong history of performance.

Janus Henderson Enterprise D (JANEX - Free Report) : 0.81% expense ratio and 0.64% management fee. JANEX is a Mid Cap Growth mutual fund. These funds aim to target companies with a market capitalization between $2 billion and $10 billion that are also expected to exhibit more extensive growth opportunities for investors than their peers. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 14.8% over the last five years.

So, there you have it - if your advisor has you invested in any of our "Magnificent Retirement Mutual Funds," they are certainly earning their keep. If not, you may want to look elsewhere.