The fund provides exposure to a variety of long-term US Treasury bonds. Securities selected are investment-grade and have more than 20 years until maturity. The index is market-value-weighted and rebalanced monthly. The fund aims to hold US Treasurys in parallel proportions as they are reflected in the index. The Manager may also opt to use a sampling strategy, which uses quant analysis to select bonds that resemble index constituents in terms of key risk factors, performance attributes, industry weightings, market capitalization and other appropriate financial characteristics. The fund is also offered as CAD-hedged units and as USD units. Sibling fund ZTM provides the same exposure but with maturities of 5-10 years while ZTS holds shorter term bonds with 1-5 years to maturity.