The castle nut is a nut with slots (notches) cut into one end.The slots can accommodate a cotter, split, or taper pin or wire, which prevents a nut from loosening.Castle nuts are used in low-torque applications, such as holding a wheel bearing in place. Sizes: Metric sizes range from M8-M72, inch sizes range from 5/16 '' to 1 1/2 ''. Package Type: carton or bag and pallet. Payment terms: T/T, L/C. Delivery Time: 30 days for one container. Trade Term: EXW, FOB, CIF, CFR.