For unscrewing and disassembly of glow plugs in the cylinder head, especially when stuck from carbonization. Eliminates need to remove cylinder head. Services 10mm glow plugs, engine codes 611, 612, 613, etc. All steel construction w/ 3/8" square drive. California prop 65 - warning, this product contains chemicals known to the state of California to cause cancer, birth defects or other reproductive harm.