Yes they are the right ones. Both Associated and Losi used a "mini" locknut in various places on their cars. This link,
http://www.amainhobbies.com/product_...rce=google_ext, is to the Losi ones which will work as well. I have 4 TC3s built and a couple more in spares and can verify they are the correct nuts. The standard size 4/40 nuts more commonly found are what is pictured above. Buy a pack because you'll want to have some extras around. They do "sneak" out unnoticed sometimes when working on motor adjustments.