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 am a Canadian customer and at first I was a little skeptical ordering but after first emailing Aaron, now I just keep coming back! Amazing customer service and shipping is fair for custom/import charges. My #1 shop for anything I'll ever need for the Mini!!!
Ralph Santos
I installed the Cravenspeed "Big Pair"today. Huge difference, just what the F56 chassis needed. Well made and very easy to install.
Peter
Very good experience. Shop, order, received the part I ordered and satisfied
That's it!