some IADC code for reference:

437 
Soft Formation TCI Tricone Bits 
The 427 tci bits are used to drill low compressive strength,very soft formations .TCI bits maximize the use of bothconical and chisel tungsten carbide inserts of large diameters and high projection.This cutting sstructure design,combined with maximum cone offset,results in high bit penetration rates .The deep intermesh of cutter rows prevents bit bailing in sticky formations. 
 517 
Medium Formation TCI Tricone bits 
The 517features aggressive chisel tungsten carbide inserts on the heel rows and inner rows.This desing provides a fast drilling rate and added cutting structure durability in medium-to medium hard formations .The HSN rubber o-ring provides adequate sealing for bearing durability. 
 637 
Hard Formation TCI Tricone Bits 
The 637bits can be used to drill hard and abrasive formations .Wearresistant tungsten carbide inserts are used in the outer rows to prevent loss of bit gauge.Maximum numbers of bemisphericalshaped inserts are used in all rows to provide cutter durability and long life. 
 617 
Medium-Hard Formation TCI Tricone Bits 
The 617features robust chisel tungsten carbide inserts on the heel row and conical on the inner rows.This design provides a fast drilling rate and added sutti8ng structure durability in medium to medium hard formations .The HSN rubber o-ring [rovodes adequate sea;omg fpr bearomg dirability.