LED (Light Emitting Diode) Christmas Lights can be identified by their lack of a filament and the presence of a T-Lock on the side of the bulb. The strand may have a RCA style jack and control box instead of a standard plug and extension cord.
LED lights on newer trees can be identified by their RCA Jack style plug and Control Box extension cord.
2012 and older Surebright light strands have fuse bulbs that are glued to the base and CANNOT be replaced. (These can be identified by a white collar around the bulb. See photo below).
The Master Fuse Bulb found on 2013-1414 manufactured trees can be replaced. Check the bulb pack that came inside your box.