Back off sub is also called back off spear.It can replace the tapertap,fishing orback off when dealing with sticking.If the fish is stuck or cannot be back off,it can release from the back off sub,and then trip the drilling tool.
| Model | OD | ID | OAL | Connection |
| mm(inch) | mm(inch) | mm (ft) | ||
| ZDK105 | 105(4-1/8) | 15(19/32) | 580(1.9) | NC31LHBox×NC31 Pin |
| ZDK121 | 121(4-3/4) | 22(55/64) | 628(2.1) | NC38LH Box×NC38 Pin |
| ZDK159 | 159(6-1/4) | 28(1-7/64) | 690(2.3) | NC46LH Box×NC46 Pin |
| ZDK165 | 165(6-1/2) | 28(1-7/64) | 690(2.3) | NC50LH Box×NC50 Pin |
| ZDK168 | 168(6-5/8) | 28(1-7/64) | 690(2.3) | NC50LH Box×NC50 Pin |
| ZDK178 | 178(7) | 32(1-1/4) | 700(2.3) | 5-1/2FH LH Box×5-1/2FHPin |
| ZDK203 | 203(8) | 35(1-3/8) | 723(2.4) | 6-5/8REGLH Box×6-5/8REG Pin |










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