The General Pump Y10321300 replaces an O-ring inside unloaders. It is designed to fit unloader models PULSAR4LP, PULSAR4HP, PULSAR4KHPEZ, YVB8KMS, and YVB75KDMN21. Made with Buna-N with a Duro 70 hardness. O-ring measures 3 x 6 mm. A genuine OEM part that ensures a proper fit when installed in the recommended models.