---Drill collar Usage : One of the most important components of the drill string is to provide drilling bit of pressure and the drill string rigid role . Standard : API 7, API 7-1 and SY/T standards. Material : AISI 4145 H or Non-magnetic material. Types: Slick drill collars Spiral drill collars Non-mag material drill collars Size : OD : 3 1/8"---11", Length : 10'---31' Mechanical Property : Mechanical Property of Slick and Spiral drill collars made of AISI 4145 H