4" Tri-Cone Drill Bit   2 3/8" A.P.I. PIN CONNECTION  Available from Soft to Hard Formation     Tricone Steel Mill Tooth Rock Bits         TR3 (IADC  1-2-1)   Soft to Medium Formations The TR3 is the fastest drilling bit produced by A & D Drilling Supply Corp. . This bit model is designed with long "A" shaped teeth, widely spaced and fully hard faced from crest to root for maximum penetration rates. In formations that range from moderately soft to medium soft. This design is most effective in formations with compressive strengths under 5,000, such as shale, clay, red bed, medium limestone and unconsolidated formations. The TR3 also features the absence of deletions on the gage side of teeth on the heel row of the number two cone. This insures maximum gag