New Pat-Pending Fail Safe Heat Treated Alloy 2 1/2″ Hex Hub Specifically Designed To Provide High Levels Of Safety Factor For Digger Derrick Auger Drills While eliminating Possible Failures Of The Industries Butt Welded Hubs Of The Past. Lateral And Torsional Failures Have Been Designed Out Of this New Product. Fail Safe Design – 4″ OD Boss Design Eliminates Butt Welding While Provides Highly Accurate Self Aligning Design- For Use With 4″ x 3/8″ DOM Tubing.