This 4-pin CDI is very hard to find.  It is similar to many of the other cdi s you see but has a 4-pin almost square plug.  

CDI description:

• 4-pin (plug as pictured)
• 59.8mm long (2.35 in)
  
• 34.7mm wide (1.37 in)
  
• 22.3mm height (0.88 in)
  
• Comes with mounting strap

• Known to fit Coolster, Redcat, and Tao Tao, along with many other manufacturers. 

  Shipping details:

  Do you need your CDI fast?  If you order before 3:00 pm CST, Monday thru Friday, your order goes out the same day.  Buy now!

  Electrical parts are not returnable.  Please double check before ordering.