According to it's maker: Studio 1AM, the "Cork Cuff explores natural cork as a wearable material. 100% recycled and recyclable, flexible, and water repellent, cork is the perfect unexplored resource for jewelry." It even comes with a docking station......$48.00
As far as concrete cufflinks go, I think that these are my favorites. Like the others, they are simple and modern - with the perfect contrast the concrete adds.
I think the brilliance of putting concrete with silver is that they contrast perfectly with one another.
I certainly don't think there is anything more manly than concrete. Put concrete into cuflinks and we have the ultimate manly male fashion accessory.