Summary Prospectus

AMG SouthernSun U.S. Equity Fund

Investor Class: SSEFX

Class C: SSECX

Institutional Class: SSEIX

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Investment Objective

The AMG SouthernSun U.S. Equity Fund's (the “Fund”) investment objective is to provide long-term capital appreciation.

Fees and Expenses of the Fund

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

1	Effective May 17, 2014, the Redemption Fee will apply to redemptions made within 60 days of purchase.

¹ These amounts have been adjusted as necessary from amounts incurred during the Predecessor Fund’s (as defined below) most recent fiscal year to reflect current fees and expenses.

Expense Example

This Example will help you compare the cost of investing in the Fund to the cost of investing in other mutual funds. The Example makes certain assumptions. It assumes that you invest $10,000 as an initial investment in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. It also assumes that your investment has a 5% total return each year and the Fund’s operating expenses remain the

same. Although your actual costs may be higher or lower, based on the above assumptions, your costs would be:

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the predecessor to the Fund, SouthernSun U.S. Equity Fund, a series of Northern Lights Fund Trust (the “Predecessor Fund”), had a portfolio turnover rate of 25% of the average value of its portfolio.

Principal Investment Strategies

Under normal market conditions, the Fund invests at least 80% of its assets (defined as net assets plus any borrowing for investment purposes) in equity securities (common stocks) of U.S. companies. SouthernSun Asset Management, LLC (“SouthernSun” or the “Subadvisor”) seeks to achieve the Fund’s investment objective by investing primarily in common stocks of small to middle capitalization U.S. companies that SouthernSun selects using a research-driven, value-oriented investment strategy. The Fund defines the investable universe of small to middle capitalization securities to include securities of issuers with a market capitalization at the time of purchase within the capitalization range of companies in the Russell 2500 ^® Index and/or the Russell Midcap ^® Index during the most recent 12 month period (based on month-end data). This capitalization range will change over time. As of December 31, 2013, the range was $9.6 million to $12.7 billion for the Russell 2500 ^® Index and $296.4 million to $31.3 billion for the Russell Midcap ^® Index.

The Fund’s portfolio typically invests in 20-40 companies SouthernSun believes are niche dominant, attractively-valued with financial flexibility and uniquely-fitted management teams. When selecting companies for investment, SouthernSun seeks opportunities that it believes have the following characteristics:

•	Financial Flexibility: SouthernSun prefers companies that have strong internally generated discretionary cash flow and organic revenue growth.

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SUM064-0414

AMG SouthernSun U.S. Equity Fund SUMMARY PROSPECTUS

•	Management Adaptability: SouthernSun prefers management teams with measurable, transparent goals that are held accountable for performance. This applies to multiple levels of management from the CEO and CFO to the plant/facilities manager.
•	Niche Dominance: SouthernSun prefers companies that it believes exhibit competitive advantages through superior products, process controls and technologies.

The Fund generally seeks to buy and hold stocks for the long-term, but will sell holdings that SouthernSun believes have exceeded their intrinsic market value, become too large a position, experienced a change in fundamentals or are subject to other factors that may contribute to relative under performance. The Fund generally seeks to hold positions in companies as they increase in market capitalization as long as SouthernSun considers the company to remain an attractive investment with capital appreciation potential.

The Fund is non-diversified, which means that it can invest a greater percentage of its assets in any one issuer than a diversified fund.

Principal Risks

There is the risk that you may lose money on your investment. All investments carry a certain amount of risk, and the Fund cannot guarantee that it will achieve its investment objective. An investment in the Fund is not a deposit or obligation of any bank, is not endorsed or guaranteed by any bank, and is not insured by the Federal Deposit Insurance Corporation (“FDIC”) or any other government agency. Below are some of the risks of investing in the Fund. The risks are described in alphabetical order and not in the order of importance or potential exposure.

Focused Investment Risk —a greater percentage of the Fund’s holdings may be focused in a smaller number of securities which may place the Fund at greater risk than a more diversified fund.

Liquidity Risk —particular investments, such as illiquid securities, may not be able to be sold at the price the Fund would like or the Fund may have to sell them at a loss.

Management Risk —because the Fund is an actively-managed investment portfolio, security selection or focus on securities in a particular style, market sector or group of companies may cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective. There can be no guarantee that the Subadvisor’s investment techniques and risk analysis will produce the desired result.

Market Risk —market prices of securities held by the Fund may fall rapidly or unpredictably due to a variety of factors, including changing economic, political, or market conditions.

Non-Diversified Fund Risk —the Fund is non-diversified and therefore a greater percentage of holdings may be concentrated in a small number of issuers or a single issuer, which can place the Fund at greater risk.

Small- and Mid-Capitalization Stock Risk —the stocks of small- and mid-capitalization companies often have greater price volatility, lower trading volume, and less liquidity than the stocks of larger, more established companies.

Value Stock Risk —value stocks may perform differently from the market as a whole and may be undervalued by the market for a long period of time.

Performance

The following performance information illustrates the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s performance compares to that of two broad-based securities market indices. As always, past performance of the Fund (before and after taxes) is not an indication of how the Fund will perform in the future.

The performance information shown for the Fund is that of the Predecessor Fund, which was reorganized into the Fund on March 31, 2014, and was managed by SouthernSun with the same investment objective and substantially similar investment strategies as those of the Fund.

The performance information shown assumes that all dividend and capital gain distributions have been reinvested for the Fund and, where applicable, for the indices shown in the table. The information in the bar chart is for Investor Class shares of the Fund. Class C and Institutional Class shares would have similar annual returns as Investor Class shares because all of the classes are invested in the same portfolio of securities. However, because Class C and Institutional Class shares are subject to different expenses than Investor Class shares, Class C and Institutional Class share performance varies. The performance information also reflects the impact of the Fund’s previous contractual expense limitation. If the Predecessor Fund’s investment manager had not agreed to limit expenses, returns would have been lower.

To obtain updated performance information please visit or call 800.835.3879.

Calendar Year Total Returns as of 12/31/13 (Investor Class)

Best Quarter: 13.97% (3rd Quarter 2013)
Worst Quarter: 2.87% (2nd Quarter 2013)

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2	Managers Investment Group

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