NEW YORK ( TheStreet) -- The ETF industry will take another swipe at mutual funds with the release of four active ETFs from Grail Advisors today.The actively managed funds -- RP Growth, RP Focused Large Cap Growth, RP Technology and RP Financials -- are designed to challenge the established world of actively managed mutual funds. Will the release of the new active ETFs signal the death of mutual funds? Not so fast. Grail's first active ETF offering, the Grail American Beacon Large Value ETF ( GVT), has just $3 million in assets. Actively managed products from PowerShares have also struggled to take hold. Retirement investing is a trillion dollar industry dominated by money managers, 401(k) and pension plans, and buy-and-hold strategies. It is also an industry that has long been dominated by mutual funds. It is no wonder that the booming ETF industry is looking to swipe a piece of the retirement investing pie. ETF investors often highlight the differences between ETFs and mutual funds to make the case for ETF superiority. ETFs are traded throughout the trading day, unlike mutual funds, making it easy for investors to trade in and out of positions. ETFs also have lower fees and higher transparency, making their strategies accessible. While these differences have helped the ETF industry grow at such an amazing rate, these differences will make it particularly difficult for actively managed ETFs to target actively managed mutual funds and succeed. ETFs and mutual funds trade in different ways -- a key difference that threatens the success of active ETFs the most. Mutual funds are priced once a day, and buyers and sellers are sure to get that price, which represents the value of the underlying portfolio.