60,000 PSI tensile ductile iron body parts for mass and strength. Extra deep throat - this design gives you more working room where it counts. Hardened steel jaw, replaceable inserts are machine serrated for safe, sure grip under maximum torque. Large anvil. Locking swivel base - 360º rotating is enhanced by serrated swivel base with double lockdowns for non-slip holding and four mounting posts. Precision thrust bearing creates greater clamping pressure and increased longevity.