Specialty jam nuts have smaller outside diameters allowing smaller wrenches to be used when changing radius rod lengths. 1/2 bolts the same 3/4 wrench can be used to adjust radius rod or mounting hole locations. Features. 18 Left Hand Aluminum Thin OD Jam Nuts. High quality construction and durability. Variety of styles for every type of accessory. Pack of 4Specifications. Color Black. Size 0.63. Material Aluminum