Water-tight Christmas tree light

A water-tight Christmas tree light comprising:

• a lamp socket having an outward flange around one end thereof, an outside annular surface defining a lamp socket periphery, an outer projecting wall raised around the lamp socket periphery, said outward flange and said outer projecting wall defining an outside annular groove therebetween;
• a lamp bulb fastened to said lamp socket, said lamp bulb having a lamp bulb periphery;
• and
• a rubber sealing cap having a tapered, hollow, cylindrical cap body mounted on said lamp socket around said lamp bulb to seal a gap between said lamp socket and said lamp bulb, a first cap end and a second cap end opposite said first cap end, an inward top flange on said first cap end pressed on said lamp bulb periphery, a chamfered bottom edge on said second cap end forced into the outside annular groove of said lamp socket, an inside annular flange disposed between said inward top flange and said chamfered bottom edge, and an inside projecting wall disposed between said inside annular flange and said chamfered bottom edge, said inside annular flange being stopped against and between said inside projecting wall and said lamp socket periphery, and an inside annular groove defined within said cap body and said inside projecting wall to snugly receive the outer projecting wall of said lamp socket.