Designed to provide broad exposure to the Style Box - Mid Cap Growth category of the market, the Invesco S&P MidCap 400 Pure Growth ETF (RFG) is a smart beta exchange traded fund launched on 03/01/2006.What Are Smart Beta ETFs?Products that are based on market cap weighted indexes, which are strategies designed to reflect a specific market segment or the market as a whole, have traditionally dominated the ETF industry.Market cap weighted indexes work great for investors who believe in market efficiency. They provide a low-cost, convenient and transparent way of replicating market returns.On the other hand, some investors who believe that it is possible to beat the market by superior stock selection opt to invest in another class of funds that track non-cap weighted strategies--popularly known as smart beta.This kind of index follows this same mindset, as it attempts to pick stocks that have better chances of risk-return performance; non-cap weighted strategies base selection on certain fundamental characteristics, or a mix of such characteristics.While this space offers a number of choices to investors, including simplest equal-weighting, fundamental weighting and volatility/momentum based weighting methodologies, not all these strategies have been able to deliver superior results.Fund Sponsor & IndexRFG is managed by Invesco, and this fund has amassed over $396.97 million, which makes it one of the average sized ETFs in the Style Box - Mid Cap Growth. This particular fund, before fees and expenses, seeks to match the performance of the S&P MidCap 400 Pure Growth Index.The S&P MidCap 400 Pure Growth Index measures the performance of securities that exhibit strong growth characteristics in the S&P MidCap 400 Index.Cost & Other ExpensesSince cheaper funds tend to produce better results than more expensive funds, assuming all other factors remain equal, it is important for investors to pay attention to an ETF's expense ratio.Annual operating expenses for this ETF are 0.35%, making it on par with most peer products in the space.It's 12-month trailing dividend yield comes in at 0.05%.Sector Exposure and Top HoldingsMost ETFs are very transparent products, and disclose their holdings on a daily basis. ETFs also offer diversified exposure, which minimizes single stock risk, though it's still important for investors to research a fund's holdings.This ETF has heaviest allocation in the Consumer Discretionary sector - about 23.60% of the portfolio. Healthcare and Information Technology round out the top three.Taking into account individual holdings, Digital Turbine Inc (APPS) accounts for about 3.35% of the fund's total assets, followed by Repligen Corp (RGEN) and Rh (RH).The top 10 holdings account for about 25.25% of total assets under management.Performance and RiskYear-to-date, the Invesco S&P MidCap 400 Pure Growth ETF has gained about 14.45% so far, and was up about 12.48% over the last 12 months (as of 12/29/2021). RFG has traded between $200.22 and $245.79 in this past 52-week period.RFG has a beta of 1.17 and standard deviation of 27.59% for the trailing three-year period, which makes the fund a medium risk choice in the space. With about 83 holdings, it effectively diversifies company-specific risk.AlternativesInvesco S&P MidCap 400 Pure Growth ETF is a reasonable option for investors seeking to outperform the Style Box - Mid Cap Growth segment of the market. However, there are other ETFs in the space which investors could consider.Vanguard MidCap Growth ETF (VOT) tracks CRSP U.S. Mid Cap Growth Index and the iShares Russell MidCap Growth ETF (IWP) tracks Russell MidCap Growth Index. Vanguard MidCap Growth ETF has $12.58 billion in assets, iShares Russell MidCap Growth ETF has $16.19 billion. VOT has an expense ratio of 0.07% and IWP charges 0.23%.Investors looking for cheaper and lower-risk options should consider traditional market cap weighted ETFs that aim to match the returns of the Style Box - Mid Cap Growth.Bottom LineTo learn more about this product and other ETFs, screen for products that match your investment objectives and read articles on latest developments in the ETF investing universe, please visit Zacks ETF Center. Want key ETF info delivered straight to your inbox? Zacks’ free Fund Newsletter will brief you on top news and analysis, as well as top-performing ETFs, each week.Get it free >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Invesco S&P MidCap 400 Pure Growth ETF (RFG): ETF Research Reports Repligen Corporation (RGEN): Free Stock Analysis Report RH (RH): Free Stock Analysis Report iShares Russell MidCap Growth ETF (IWP): ETF Research Reports Digital Turbine, Inc. (APPS): Free Stock Analysis Report Vanguard MidCap Growth ETF (VOT): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research