Jeff and Alan, I only want to add that people with neck and back issues should use the trend from a friend prior to purchasing one. I tried everything to balance mine but found I could get it balanced in one stance but not another. I couldn't wear mine for more than ten to fifteen minutes before my neck hurt so bad that I would have to take a long break or quit for the day. Thus it became a dust collector and not a dust collector for my lungs sake. I finally sold it for a $100 loss and found something that works. Many people swear by it, which is great, but try it first to insure that your neck and back can tolerate it.