Drill collars
Drill collar is mainly used to provide bit weight to drill bit so that drill pipe is in tension. Especially drill collar can keep drill bit centralized and hole tract by large rigidity. Manufactured strictly from API Spec 7.

Size from 3-1/8" to 11"
Type: Normal drill collars, Non-magnetic drill collars, Spiral drill collars
Material: AISI 4145H
Length 9.15m, 9.45m