Vigor's Drill Collar is made from forged solid steel bar, in material AISI 4145H and modified alloy steel, heat treated to API standards, mechanical properties guaranteed 1" below surface. End connection is done by CNC machines, thread roots are cold rolled to imporve fatigure resistance, Pin relief groove and Box bore back featureis are available. All connections are equipped with pressed steel thread protectors. Standard: API Spec.7-1 and NS-1 Material: AISI 4145H and AISI 4145H Mod. Non-magnetic material Types: Slick Drill Collar Sprial Drill Collar Short Drill Collar Special Feature: Threads Cold rolled. Pin relief Groove and Box Bore back. Benchmark Slip and Elevator Recess Hardbanding