The BlueSpot 9 PCE 1/4"-3/8"-1/2" Mixed Extension Bar Set is manufactured from chrome vanadium for increased durability. Each extension bar has a knurled non-slip finger grips on the shafts for extra grip. Spring-loaded ball bearing for secure socket holding.Package Contents - 1/4'' - 50mm, 100mm, 225mm. 3/8''- 75mm, 150mm, 225mm. 1/2'' - 50mm, 125mm, 250mm.Manufactured from chrome vanadium for increased durabilityKnurled non-slip finger grips on shaftsSpring ball socket retentionSupplied in EVA foam tray