An ETF that has sprung to life in recent sessions is iShares S&P 100 (NYSEArca: OEF), which has been around since the year 2000, making it a “trailblazer” in some sense to those portfolio managers today that followed ETFs way back then.

Since inception, the fund has gathered more than $4 billion in assets under management, and on an average daily basis the ETF trades about 990,000 shares per day.

In the past several days, OEF has accumulated more than $700 million in new assets, and given its current asset base, this represented more than 20% of the assets outstanding in the ETF. OEF, as its name suggests, tracks the S&P 100 Index which is designed as a “Mega Cap” index, including the “largest” large cap names.

All 100 holdings in OEF are included in the S&P 500 Index, which we will represent with IVV (iShares S&P 500) for this example. It is fair to say that the S&P 100 is a subset of the S&P 500 in fact.

Year to date, OEF has displayed out-performance versus the benchmark S&P 500 Index, as OEF has rallied 9.22% versus IVV rising 7.95%. Currently, top holdings of OEF are AAPL (7.05%),  XOM (4.85%), IBM (2.93%), MSFT (2.85%), and T (2.65%) versus IVV with the same top five holdings just with lesser weights in all of them due to the fact that the index holds 500 names instead of the 100 as in OEF.