kelly with packing barrel: 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.