This replacement part is a factory original from Glock. Factory replacement parts are manufactured to the exact same specifications and tolerances and use the same manufacturing materials as the original parts which guarantees excellent fit and reliable operation. Some parts may need to be installed by a qualified gunsmith.Notes: Glock made a running change with their triggers a number of years ago beginning with serial numbers starting with EH. This trigger is compatible with the Pre-EH serial number Glock 19.