My tree is three years old and now half the bulbs do not light. The customer service is not technical help and no one there can even explain the master bulb in a string with fuses. I am tired of talking to them, they are sending me a new light string but can not help me find the problem and fi the ones I have. There are not tools on the market to test ad repair their lights because they are unique. User's recommendation: Do not buy Balsam hill products.