The fund provides exposure to USD-denominated investment-grade corporate bonds, with a minimum of three years to maturity. The index, which is weighted by market value and capped at 3% per issuer, is designed to represent what are perceived to be the most liquid investment-grade corporate bonds available. The fund selects fixed coupon bonds, step-up bonds with coupons schedules known at issuance, sinking funds and amortizing bonds, medium-term notes, Rule 144A offerings with a registration right, callable, and puttable bonds. Excluded are convertible and preferred shares or bonds with other equity features attached. The fund may invest in one or more iShares ETFs, or may utilize a representative sampling approach in which securities are chosen to provide the same investment characteristics as the index. The index is rebalanced monthly.