This is a Rival Arms Part known as the 19, model RA50G201S.
Experienced shooters realize plastic guide rods can chip" crack" or break resulting in feeding or ejection failures. Flex can also contribute to accuracy problems. Rival Arms Guide Rod Assemblies address all of these issues and will provide you a lifetime of reliable service.
Features:
Premium Spring (Stock Weight)
Stainless Steel
CNC-Machined