Large anvil. 60,000 PSI tensile ductile iron body parts for mass and strength. Self-centering pipe jaws - hardened steel jaws hold up to 6" pipe safely, securely. Hardened steel jaw inserts - machine serrated, replaceable jaws assure a positive hold. Locking swivel base - with double lockdowns for non-slip hold in any position. Precision thrust bearing creates greater clamping pressure and increased longevity