Looking for castle nuts? for Sharktooth turn signals

[340wedge]

Does anyone know where to find these nuts? Thank you.

 

[Jadaharabi]

Ace hardware.

 

[Daves69]

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Mr. G's Enterprises - Auto Fasteners

Mr. G's Enterprises refurbishes plastic, makes screw and bolt kits, and has an 8,000,000 auto fastener inventory.

mrgusa.com

 

[ACME SS]

So those are called thread cutting nuts or single thread nuts. A castle nut is for use with a cotter pin or lock wire and looks like this. Helps in finding them online if you don't have a store nearby.