XLRE tracks a market cap-weighted index of REITs and real estate stocks, excluding mortgage REITs, from the S&P 500. XLRE represents the new real estate sector concentrated portfolio of mostly large-caps . XLF provided roughly $3B in AUM in the form of REITs to XLRE in return for its shares, which were then distributed to XLF shareholders, thus providing a massive boost to XLRE’s AUM.