Hex jam nylon insert lock nuts, Stainless steel 316, Coarse (standard) thread, 1/2"
Nut size (A.K.A. diameter) is the size bolt that the nut is used with. The same is true of the thread count. Thus a 1/4"-20 nut fits a 1/4"-20 bolt.
Note: Stainless lock nuts may require extra care during installation to avoid galling (seizing up). More info.