FAG KM8 Locknut, Standard, Right Hand, Metric, 40mm ID, 58mm OD, 6mm Width, 1.5mm Pitch

Amazon

Locks bearings onto shafts or adapter sleeves so that bearings stay in place Four evenly spaced slots on circumference for hook or striking-face wrenches to tighten locknut into place Steel for durability and resistance to deformity under heavy loads Right-handed with 12 threads per inch Dimensions and material conform to DIN 981 and ISO 2 982-2 for quality assurance

Radwell UK

KM SERIES BEARING LOCK NUT - M40X1.5 MM THREAD SIZE, 58 MM OD, 50 MM FACE DIA., 9 MM WIDTH, STEEL