PURPOSE: To provide a protective bellows of EPDM-polypropylene useful as a protective bellows for an automotive steering mechanism or the like.

CONSTITUTION: This bellows comprises a fixing collar 12 for gripping the outside of a casing 18 of a steering mechanism, and a fixing collar 14 for gripping a surface 20 to be mounted with a steering rod 16. The bellows is manufactured of EDPM-polypropylene or similar thermoplastic material in a blow molding method. Compared to conventionally used material, it has a smaller elasticity, so an initial diameter of the fixing collar 14 is decided based on a ratio of a diameter of a boss 22 to the mounting surface 20 so that pressurizing force of the fixing collar 14 to grip the mounting surface 20 provides sufficient gas tightness initially and during an expected durable period of the bellows.