Several abbreviations are used to designate alternator type, condition and accessories. The letter R at the end of the part number means the alternator has been overhauled. This will also show up in the description as OHC. The absence of an R or the letter L means the unit is new. Units are sold as outright, meaning there is no core charge and no core is expected in return. If the description shows EXCH, then a core charge will be invoiced and an acceptable core is expected in return. The letters BD means belt drive and GD means gear drive. S or P means no pulley is supplied, so remove your pulley when sending in a core. B is used to designate back strap.