The JPMorgan BetaBuilders Japan ETF BBJP, launched on Jun 15, has been surging in popularity with its assets growing more than 10,900% over the past week. This is especially true, as the fund has amassed nearly $1.16 billion in AUM since Jul 13, sending its total AUM to $1.18 billion.With this, BBJP becomes the second-fastest ETF to reach the $1 billion milestone, only behind SPDR Gold Trust GLD, which touched that level in three days, and ahead of the PIMCO Active Bond ETF BOND, which did it in less than three months. If this supercharged pace of inflows continues, then BBJP could hit $2 billion by next week per etf.com, edging past GLD, which took two months to reach the mark (read: Top 5 Foreign ETFs of Q2).Given the incredible success, it is worth shedding light on some of the key aspects of the fund and comparing it with the other plain vanilla peers in the space.Low Fee: A Big AttractionThe biggest growth came on the back of the ongoing price war, which has been the hottest theme in the ETF industry and issuers are rushing to cut fees in order to garner a larger slice of the fast-growing market. The BetaBuilders brand comes with a low expense ratio of 0.19% -- 30 bps lower than the ultra-popular iShares MSCI Japan ETF EWJ.Only Franklin FTSE Japan ETF FLJP and Xtrackers Japan JPX-Nikkei 400 Equity ETF JPN are cheaper with an expense ratio of 0.09% each.Low Trading CostThe new fund trades in a solid average daily volume of 4.3 million shares, suggesting no additional cost in the form of bid/ask spread (see: all the Developed Asia-Pacific ETFs here).Higher Diversification BenefitsThough BBJP's portfolio looks almost identical to EWJ, with Toyota Motor TM as the top firm, it enjoys relatively higher diversification benefits holding 380 securities. In comparison, EWJ has 322 stocks in its basket.The new fund from JP Morgan JPM seeks to provide exposure to the broad Japanese equity market using a "passive" investment approach. It tracks the Morningstar Japan Target Market Exposure Index, which is a free-float adjusted market-cap weighted index consisting of stocks traded primarily on the Tokyo and Nagoya Stock Exchanges. On the other hand, EWJ follows the MSCI Japan Index, which is designed to measure the performance of the large and mid-cap segments of the Japanese market and selects only Tokyo-listed stocks (read: 4 Reasons Why Investors Love Passive ETFs).However, sector-wise, both funds allocate at least 20% each in industrials and consumer discretionary while financials and information technology round off the next two spots, with double-digit exposure each.Monetary Policy ChangeBBJP growth also comes following the speculation that Bank of Japan (BOJ) is looking to modify its monetary easing policy. Per Reuters, BOJ is holding preliminary discussions on possible changes to its monetary policy, which include adjustments to interest-rate targets and stock-buying techniques and focus on ways to make the massive stimulus program more sustainable in the long term. The changes could be implemented as early as in its meeting next week (read: Focus on Small Cap ETFs for Japan Exposure).As inflation remained well below the BOJ's target of 2% even after the central bank bought more than 40% of government debt since 2013, the central bank could change its way of purchasing government bonds or exchange-traded funds.Though the news has bolstered the already strong Japanese yen, taking a toll on exporters, it might not be as bad as it appears. This is because the U.S. dollar is set to accelerate against the basket of currencies given the Fed’s hawkish stance on rates hike.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 JPMorgan Chase & Co. (JPM): Free Stock Analysis Report Toyota Motor Corporation (TM): Free Stock Analysis Report GOLD (LONDON P (GLD): ETF Research Reports ISHARS-JAPAN (EWJ): ETF Research Reports PIMCO-TOT RETRN (BOND): ETF Research Reports FL-FTSE JAPAN (FLJP): ETF Research Reports DEUTS-XT JP N4 (JPN): ETF Research Reports JPM-BBLD JAP (BBJP): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research 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