spiral drill collars 1.standard:API,SY/T5144,AISI 4145H 2.the best ... .delivery promptly 4.high quality service Spiral drill collarsThe drill collars are made of 4145H modified chromium-molybdenum alloy steel according ... .59279.41111.9±2.3720378.7±1.59Note:spiral drill collars has spiral grooves, right hand, well distributes spiral drill ...