Cyclic polymers are gaining interest as novel materials with distinct properties compared to linear polymers. Industrial-scale control of their molecular weight and dispersion poses challenges. Cyclic (alkyl)(amino)carbene (cAAC) ligands are promising catalysts for olefin metathesis, and we present a successful cAAC-based ring-expansion metathesis polymerization (REMP) catalyst. A notable feature is its effortless optimization of the polymerization by adjusting the alkyl chain length. Moreover, it remains stable in ambient air, facilitating easy handling during polymerization.