The Stop Shop is your complete source for automotive hardware, tubing, tools and much more. If you have any questions at all, feel free to message us.  These plugs work great for brake line applications where you need to plug off any 9/16"-18 & 1/2"-20 spots, usually used on blocks or master cylindersHigh quality steel, 2 of each size 9/16"-18 & 1/2"-20,