This is a Hot Racing Arrma 4x4 BLX Steel Helical Diff Ring and Pinion, an optional steel helical spiral 37T/13T gear set for Arrma 1/10 4WD. The 37T/13T gear set is the stock gear ratio.
 
Features:
Precision machined helical spiral cut gears offer inherently greater strength and smooth operation than the factory bevel gears. (it has been updated to 15g lighter)
High carbon steel construction
Stronger than the stock bevel Plastic gears
Maintains the stock 37T/13T ratio
Specifications:
Weight: 32.35oz (66.75g)
 
Includes:
(1) 37 tooth diff spiral cut ring gear
(1) 13 tooth spiral cut pinion gear
Notes:
To be used with ARAC4023 Composite Diff case Cover Or HRAATF11A01 Aluminum Diff case Cover.