1. Build quality. Simply superb, as one expects from an “L” lens. The zoom and focus rings are silky smooth. 2. Optical quality. Very sharp throughout the zoom range. Not quite as sharp as my 70-200 f2.8L, probably due to the extra two lens elements for the Image Stabilization system (my 70-200 is the non-IS version).
https://www.amazon.com/Canon-24-105mm-USM-Lens-Cameras/dp/B000AZ57M6

