The standard for face-grain bowl work in almost all English speaking countries in the world.  Made from a 5/8" diameter round rod, 1/2" across the flutes. Unhandled. 
Made by Hamlet of Sheffield England in high speed steel, this is a powerful size to do almost any size face-grain bowl--from 5" to 30" in diameter.   The sizing is the English method:  outside of one flute to the inside of the other--so this is called a "1/2"  gouge but is made from a 5/8" round rod.  The overall length is 12", with the flute around 6.5" in length.  This is the unhandled  version:  I recommend a 16" to 18" long handle.  Visit my site www.alanlacer.com   and look under "Articles" to find info on handle making.