49 CFR 585.135: Scope.

This subpart establishes requirements for manufacturers of passenger cars, and of trucks and multipurpose passenger vehicles with a gross vehicle weight rating (GVWR) of 3,855 kilograms (8,500 pounds) or less, and of buses with a GVWR of 4,536 kg (10,000 lb) or less, to submit a report per § 585.140, and maintain records related to the report according to § 585.141, concerning the number of such vehicles that meet the requirements of Standard No. 225, Child restraint anchorage systems (49 CFR 571.225).