I finally got a chance to take the YKS headlamp out for a field test. It is a slick looking device and weighs in at a light weight 3.7 oz. That is a bit more than the Petzl Zipka at 2.3 oz. Maybe the added features of the YKS are worth the extra ounce over the Petzl. Both use 3 AAA batteries, so the battery weight is the same.
The YKZ has an elastic headband that was very comfortable. The single LED light mounts on a base that allows tilting, so the light can be adjusted to whatever angle the wearer chooses. The light uses a single LED, and has high, low, and blinking settings. The light is also adjustable in beam width, and the beam has a very sharp edge. Very little light falls outside of the circular beam, so the light in the beam is the most efficient possible. The photo below shows that the light beam is very focused, and the width of the light beam is adjustable.
I wondered if the light was water resistant, and thought, there is one way to find out. The picture below is the headlamp on, in the lake where I was camped. I left it in the lake, in about 10 inches of water, for about a minute and it worked fine underwater. I don’t think I want to try that with most head lamps. I used it for the rest of the evening, and during the night, and it worked fine. I would not advise putting the light in water, but it seems to be at least water resistant.
There is a red band of clear red plastic around the lens, and when the light is on that red band is visible to the side. These sell on ebay for $5 to $20, and seems like a great headlamp for that price.