The funds in our "Magnificent Retirement Mutual Funds" list are some of the top-performing, best managed funds available. If you're already invested in them, congratulations! If you're not, don't worry - it's never too late to start getting the advantages of these outstanding funds for your retirement.The easiest, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Our Zacks Rank covers over 19,000 mutual funds has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.Let's learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.AB Large Cap Growth K (ALCKX) has a 0.95% expense ratio and 0.51% management fee. ALCKX 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 yearly returns of 15.92% over the last five years, this fund clearly wins.William Blair Global Leaders Institutional (BGGIX): 0.9% expense ratio and 0.85% management fee. BGGIX is a Global - Equity mutual fund. These funds invest in large markets like the U.S., Europe, and Japan, and operate with very few geographical limitations. With yearly returns of 10.07% over the last five years, BGGIX is an effectively diversified fund with a long reputation of solidly positive performance.Fidelity Advisor Semiconductors I (FELIX): 0.81% expense ratio and 0.54% management fee. FELIX is part of the Sector - Tech mutual fund category that invests in technology and lets investors own a stake in a notoriously volatile sector, but with a much more diversified approach. With a five-year annual return of 22.21%, this fund is a well-diversified fund with a long track record of success.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.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 (ALCKX): Fund Analysis Report Get Your Free (FELIX): Fund Analysis Report Get Your Free (BGGIX): Fund Analysis Report To read this article on Zacks.com click here. Zacks Investment Research