Branches are UV protected for indoor/outdoor use. Pre-lit with CLEAR C7 bulbs.  Trees are professionally lit so lights are distributed generously and evenly on every radiant branch. Trees are built using only flame-resistant materials. Heavy-duty metal hinges and brackets insure branches stay in place for years. Tough and durable cartons are perfect for storing trees after the season. Each lamp shines with rich color and remarkable intensity for more than 3,000 hours. Plus, the string stays lit if one bulb goes out. Patented external lamp block prevents loose connections – the most common cause of light set failure. Locked in their sockets, lamps will not come loose. Safety Certified. Lights are UL listed.