IYZ covers the telecommunications segment of the US large-cap equity market. It holds a concentrated portfolio of firms involved in telecom equipment and telecom service providers such as cable television services. The underlying index is part of Russells US large cap sector indicesa series of representative indices that integrates ICBs sector classification framework on Russell 1000. Holdings are market-cap-weighted, subject to regulatory capping which limits single security weights at 22.5% and aggregate weight of securities exceeding 4.5% allocation at 45%. Index rebalancing occurs quarterly. Prior to September 20, 2021, the fund tracked the Dow Jones US Select Telecommunications Index.