Comparison of original cat-to-header joint fasteners. There is a stray new nissan turbo stud I got that I was going to use before opting for all stainless here also. The demon bolts came loose with a snap like I broke the bolt but just "broke" loose. Notoriously difficult. For some reason one stud is 55mm long and the other is 48mm. They are all 1.5 pitch for the flange thread and 1.25 for the nut, all M10.