In Canada, regular bleach is 5.25% and Ultra bleach is 6% as described above, but in the U.S., Clorox Regular bleach is 6% and identified as such on the bottle (which also says "5.7% Available Chlorine") while off-brand Ultra bleach is usually 6%, but not often marked, and off-brand Regular bleach is often 3% or lower. So it's best to stick with Clorox Regular or an possibly an off-brand Ultra bleach.

Richard