The settings on my 553R's gas valve are 1.2, 1.3, 1.4 and 1.5.

For 922(r) compliance parts you can also use a US flash hider and/or a trigger from a Sig 556 rifle. The triggers are identical, so don't worry about them being of less quality. I bought a bunch when they were available as spares. They came in bags marked "made in USA".