Designed to provide broad exposure to the Mid Cap Blend segment of the US equity market, the First Trust Mid Cap Core AlphaDEX ETF (FNX) is a passively managed exchange traded fund launched on 05/08/2007.The fund is sponsored by First Trust Advisors. It has amassed assets over $1.06 billion, making it one of the average sized ETFs attempting to match the Mid Cap Blend segment of the US equity market.Why Mid Cap BlendMid cap companies, with market capitalization in the range of $2 billion and $10 billion, offer investors many things that small and large companies don't, including less risk and higher growth opportunities. Thus they have a nice balance of growth potential and stability.Typically holding a combination of both growth and value stocks, blend ETFs also demonstrate qualities seen in value and growth investments.CostsSince 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 0.59%, making it one of the more expensive products in the space.It has a 12-month trailing dividend yield of 0.94%.Sector Exposure and Top HoldingsETFs offer a diversified exposure and thus minimize single stock risk but it is still important to delve into a fund's holdings before investing. Most ETFs are very transparent products and many disclose their holdings on a daily basis.This ETF has heaviest allocation to the Financials sector--about 19.50% of the portfolio. Industrials and Consumer Discretionary round out the top three.Looking at individual holdings, Avis Budget Group, Inc. (CAR) accounts for about 0.48% of total assets, followed by Apa Corporation (APA) and Ovintiv Inc. (OVV).The top 10 holdings account for about 4.21% of total assets under management.Performance and RiskFNX seeks to match the performance of the Nasdaq AlphaDEX Mid Cap Core Index before fees and expenses. The NASDAQ AlphaDEX Mid Cap Core Index is an enhanced index which employs the AlphaDEX stock selection methodology to select stocks from the NASDAQ US 600 Mid Cap Index.The ETF has added roughly 26.69% so far this year and was up about 24.76% in the last one year (as of 12/31/2021). In the past 52-week period, it has traded between $81.91 and $107.11.The ETF has a beta of 1.27 and standard deviation of 27.85% for the trailing three-year period, making it a medium risk choice in the space. With about 452 holdings, it effectively diversifies company-specific risk.AlternativesFirst Trust Mid Cap Core AlphaDEX ETF carries a Zacks ETF Rank of 3 (Hold), which is based on expected asset class return, expense ratio, and momentum, among other factors. Thus, FNX is a good option for those seeking exposure to the Style Box - Mid Cap Blend area of the market. Investors might also want to consider some other ETF options in the space.The Vanguard MidCap ETF (VO) and the iShares Core S&P MidCap ETF (IJH) track a similar index. While Vanguard MidCap ETF has $56.78 billion in assets, iShares Core S&P MidCap ETF has $68.21 billion. VO has an expense ratio of 0.04% and IJH charges 0.05%.Bottom-LinePassively managed ETFs are becoming increasingly popular with institutional as well as retail investors due to their low cost, transparency, flexibility and tax efficiency. They are excellent vehicles for long term investors.To 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 First Trust Mid Cap Core AlphaDEX ETF (FNX): ETF Research Reports Avis Budget Group, Inc. (CAR): Free Stock Analysis Report APA Corporation (APA): Free Stock Analysis Report iShares Core S&P MidCap ETF (IJH): ETF Research Reports Vanguard MidCap ETF (VO): ETF Research Reports Ovintiv Inc. (OVV): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research