HDD Hole Openers with Replaceable Stabilizers

Stabilizer is helpful to keep hole openers at stable status in drilling, it can benefit at least 3 below aspects:
1>Extend working life of hole openers.
2>Speed up penetration rate.
3>Keep the most round shape of final hole.
 
Traditional HDD hole openers has fixed stabilizers, the diameter of stabilizers always becomes to smaller and smaller in drilling, it makes jump amplitude of hole openers become bigger and bigger, drilling speed becomes slower, meanwhile the wear-speed of roller cone bits becomes faster.

Repair to maintain OD of stabilizers of hole openers is important, it is hard to repair fixed style stabilizer at drill site, replaceable stabilizer helps drillers change new stabilizers easier in the wild.
The replaceable stabilizers has two types, one is in the front, another is in the back.