* Specification: 2-1/2" 2-7/8" 3" 3-1/2" 4-1/4" 5-1/4"

* Kellys are the drive section of the whole drill stem.

* The manufacturing of the products refers to the standard of SY/T6509-2000 or API SPEC. 7-1.

* AISI4145H alloy steel is used in producing the kellys.

* Kellys'end, drive cross-section and joint are all processed and tested in terms of API.