I use 1/8" rivets. After my first bucket build, however, I started to put them together with nuts and bolts (#4 pan head) first until everything is sitting just right (ears, brow etc). After I'm happy, I replace those bolts with rivets. It just saves having to drill the rivets out if you're completely satisfied with the stance of your bucket. I've built 10 TK helmets now and while I'm pretty confident in my building prowess, I still do it this way as it only takes a couple minutes to swap in the rivets for the the nuts and bolts. Your mileage may vary....