Omega 10025B Black Hydraulic Bottle Jack - 2 Ton Capacity Machined and polished cylinders with die-cut threads provide nonabrasive leak-free durable performance Fabricated from hard cast steel with heat-treated critical stress areas Hydraulic system is protected from internal damage by a bypass mechanism US patent number: 5,946912 Unique cross-type forged release valves assures positive load control Overload protection