Those are called rivets which are extremely durable and strong when installed correctly using a rivet gun, however, standard stainless bolts and nuts sourced from a local hardware store will work just as well.
I bought Denso Iridium Colder spark plugs recently and found out that they are a horrible product to use. Wish that Outmotoring would allow customer reviews on products, that way we the consumer wouldn't have to worry able destroying our vehicles by adding sh!# parts. Why even sell this brand of spark plug if they have a bad reputation of popping out and destroying the threading!
scott
Great experience with Out Motoring. Great products, fast shipping and excellent customer service. Aaron has answered all of my questions and leveraged his experience and product knowledge to help me. Thanks!