The funds in our "Magnificent Retirement Mutual Funds" list are among the best managed and best performing mutual funds available. If you are just finding out about our Top-Ranked Funds list, we welcome you!Great performance, diversification, and low fees: it's a pretty simple formula for a great mutual fund. Some are better than others, but utilizing our Zacks Rank, we have identified three mutual funds that would make great additions to long-term investors' portfolios.Let's take a look at some of the highest Zacks Ranked mutual funds with the lowest fees.JPMorgan Mid Cap Growth Fund R2 (JMGZX): 1.49% expense ratio and 0.65% management fee. JMGZX 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. With annual returns of 11.74% over the last five years, this fund is a winner.Calvert Equity Portfolio I (CEYIX) is a stand out amongst its peers. CEYIX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. With five-year annualized performance of 14.31%, expense ratio of 0.71% and management fee of 0.6%, this diversified fund is an attractive buy with a strong history of performance.Janus Henderson Global Technology S (JATSX). Expense ratio: 1.19%. Management fee: 0.64%. Five year annual return: 23.1%. JATSX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach.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.Do You Know the Top 9 Retirement Investing Mistakes?Investing in underperforming mutual funds is just one of the key errors that can derail your retirement plans.To learn more, read our just-released report: 9 Retirement Mistakes You Need to Avoid.This report can help you sidestep these costly mistakes and potentially achieve your retirement goals. Get Your FREE Guide Now Get Your Free (CEYIX): Fund Analysis Report Get Your Free (JMGZX): Fund Analysis Report Get Your Free (JATSX): Fund Analysis Report To read this article on Zacks.com click here. Zacks Investment Research