1/2" wide. Made from solid Walnut heartwood.
This is typically what the English called "cross banding." It is simply walnut, cut at 45 degrees and edged with a light-colored wood, and was used on a lot of old English furniture. I have included (below) some pictures of the banding in a walnut box I made. The other banding used on this box (the 3/16 walnut/maple - barber-pole banding) is also available as #110 on this website.