... With Elevator Groove And Slip Groove The short drill collar produced by our company is made of ... and is accordant with mechanical property of drill collars. Besides, the connection of the drill collar is accordant with API. It ... is mainly used for connecting special tools or composing drill tools.. Normal Size Specificationmm(in)O.D.in(mm) ... (105)2(50)NC31 3,6,9,12,15,18,21,24,27 (915,1,830,2,743,3, ...