Wilwood master cylinder m10x1.0 bottom nuts for 240z, 280z, 510, 521, 620, all Japanese cars with metric hard linesthese are custom made bottom nuts that will bolt to the Wilwood 1 inch master cylinder and bolt to your original metric hardlines that are M10x1. 0 thread. Sold a s a pair of 2 pieces. Many Japanese cars use the Wilwood 1 inch master cylinder as an upgrade. Unfortunately, the Wilwood master cylinder only comes with standard thread, bottom nuts. This means the metric thread hardline that originally Threads into your original master cylinder will not