This is the aluminum idler gear for the Associated SC10 4x4 and similar trucks. 

FEATURES:

*Construction:  CNC aluminum

*Color:  silver hard anodized
*Replaces Associated 91010

YOU WILL RECEIVE:
*One 19-tooth aluminum idler gear
REQUIREMENTS:
*Installation onto vehicle
SPECIFICATIONS:
*Width:  3/8" (9 mm) 
*Outer diameter:  5/8" (16 mm)
*Inner diameter:  0.39" (10 mm)