A Regular Production Option (RPO) is a 3-digit standardized code used by General Motors to designate vehicle options & modifications. RPO codes designate how a vehicle is built, and they've been used on dealership order forms and in assembly plants since at least the 1950s (see Corvette C1). It was originally all numeric and labeled Sales Codes; in 1970 GM switched to the alphanumeric RPO code.

Even base vehicles with few optional features will have multiple RPOs, since both standard components (like engine, transmission, and paint color) and extra cost options are assigned codes.

The complete configuration of a GM vehicle (as it exited the factory) can be described by specifying the base model and a complete list of its RPO codes. Some dealerships are willing to run a VIN and print out its RPOs (with their definitions) free of charge. The records are in GMs' electronic database since at least the 1990 models. RPO decoder (for newer vehicles).

Beginning as early as 1967, and to all their models since 1984, GM attached a Service Parts Identification (SPID) label. The label is most often located on the back of the glovebox door, on the inside of the trunk lid, or on the bottom of the spare tire cover. On some of the GM SUVs and mini-vans, the SPID label will be located on one of the plastic storage covers in the rear of the vehicle.

The SPID lists, in alphabetical order, many of the options built into a vehicle, both RPOs and the older and longer Option Model#s (sometimes used before 1970). These codes are sometimes needed during vehicle repairs to select the correct replacement parts. TECH TIP: Take a photo of the Vehicle Identification Number (VIN) and the SPID with you when purchasing auto parts. NOTE: Reproduction SPID labels may be purchased online from aftermarket vendors.

In 2018, the RPO Sticker was replaced by a QR code label located on the B-pillar (driver's side, between front and rear doors). While fairly complete, it does not contain every RPO that is on the vehicle.