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.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 take a look at some of the highest Zacks Ranked mutual funds with the lowest fees.Dreyfus/Boston Small/Mid-Cap Growth Y (DBMYX) has a 0.65% expense ratio and 0.6% management fee. DBMYX 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. With yearly returns of 16.55% over the last five years, this fund clearly wins.Janus Henderson Global Technology A (JATAX). Expense ratio: 0.99%. Management fee: 0.64%. JATAX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. This fund has managed to produce a robust 21.93% over the last five years.TCW Select Equities I (TGCEX) is an attractive large-cap allocation. TGCEX 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. TGCEX has an expense ratio of 0.79%, management fee of 0.65%, and annual returns of 15.98% over the past 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.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 (DBMYX): Fund Analysis Report Get Your Free (JATAX): Fund Analysis Report Get Your Free (TGCEX): Fund Analysis Report To read this article on Zacks.com click here. Zacks Investment Research