This is the Robinson Racing 48 Pitch Extra Hard/Wide 12T Pinion Gear.      
                                                                               
FEATURES: Hardened steel construction                                          
          Fits 1/8" diameter motor shaft                                       
                                                                               
INCLUDES: 48 Pitch Extra Hard/Wide 12T Pinion Gear                             
          3mm Set Screw                                                        
                                                                               
SPECS:    Pitch: 48                                                            
          Number of Teeth: 12                                                  
          Bore: 1/8"