Kask has the best retention system of any helmet I've ever found, even the more "entry level" models, like the 50NTA. They are really comfortable, and the Kask I had did its job when called upon, I guess.

You do pay a little bit of a premium, but they do pretty much disappear on your head. No crash replacement program, which is kind of a bummer if you need it for its intended purpose too soon after buying one. 10% off for the first year after purchase would soften the blow a little.