The spigot hole in a 10 or 20 liter is ¾ inch. The 1, 2, 3 and 5 liter have a ½ inch hole. I have successfully used a threaded spigot but I imagine the unthreaded but tapered brass spigots made for wood barrels would be surer however I have not yet found a supplier where I can buy a lot of spigots so as to make it an option with all the barrels I sell. At your service Clay Johnston