HydroBlu is a well-known water filter manufacturer in the US ultralight gear scene, but almost unknown in Japan. They've won numerous awards as a water filter manufacturer, a necessity for long-distance hikers. I personally imported this along with a straw-type water filter, but I never used it and just kept it in storage. The construction is a typical trucker hat. It has an adjuster, so it fits anyone. The color is blue, reminiscent of water. A rare item that will appeal to those who love UL gear. This manufacturer will likely be mentioned when introducing water filters in the spring, so those considering a water filter might want to search for them. First come, first served! Type... Cap Gender... Unisex