HALF NUTS THIN HEXAGON LOCK NUT METRIC COARSE THREADS STAINLESS STEEL M1.6 - M36

M36 ; thread pitch; 4mm, spanner size; 55mm. M1. 6; thread pitch; 0. 35mm, spanner size; 3.2mm. A2 Stainless Steel Half Nuts. Half nuts are often used on top of a standard full nut to lock it in place.

eBay