The Aero Precision Solus Bolt Head Parts Kit has everything you need to Service the bolt head of your SOLUS rifle. IncludesExtractorExtractor Detent (2x)Extractor Spring (2x)Ejector (2x)Ejector Spring (4x)Ejector Retaining Pin (2x)Bolt Head Pin (2x)O-ring Size InformationSmall Caliber (0.382"): 223/5.56 NATO, 300 BLKStandard (0.478"): 6mm/6.5 Creedmoor, 243 Win, 308 Win, 8.6 Blackout, 270 Win, 30-06Magnum (0.540"): 6.5 PRC, 7mm SAUM, 300 WSM, 7mm WSM