Just to iron this out a bit for you fellas...
A proper US BB is not metric. The axle is actually 3/4" (19.05mm), so near as dammit and causes no problems. However, some companies have everything made in Taiwan and/or China (all metric), and have taken over the years to using some oddball sizes for things.
Stick to what you know, traditional stuff, and you'll be fine. A good ole US BB will suit Profiles or Flights no worries. That DiamondBack BB is fine for the job.