While not officially classified as an L series lens by Canon, the optics in this unit are very good. It's an excellent choice for macro work or functions well as a normal 100mm lens.
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Canon Website Description
Autofocus lens for macro photography up to life-size (1x) magnification. Inner focusing affords a long working distance of 5.9in. (149mm) at 1x. A 3-group floating system results in excellent delineation at all focusing distances. Ring USM for silent and high-speed AF, and full-time manual focusing also provided.