Hex nylon insert lock nuts, Stainless steel 18-8, Fine thread, #10

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.