In cusp reduction procedures, the contrabevel is intentionally made shorter—about one-third the length of the inside bevel—to provide a gradual transition that preserves tooth structure while effectively reducing cusp height. This careful ratio maintains adequate enamel thickness for strength and ensures better resistance form without compromising the integrity of the remaining tooth. A longer contrabevel could weaken the cusp, increasing fracture risk, whereas a shorter one optimizes stress distribution and retention of healthy tooth tissue.

Reference: Sturdevant's Art and Science of Operative Dentistry, 7th Edition.