We have a limited supply of these 5 7/8" 5- Blade bits. 5 Blades for added durability and smoother cutting over a 4-blade bit. 13mm cutters. 3 1/2" API regular pin. Carbide hard surfacing added to high wear areas. Carbide inserts on the gauge is standard. This is a great bit for drilling inside of 6" casing and for drilling geothermal holes.