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’