Bottle cap made of synthetic resin

A bottle cap made of synthetic resin comprising:

• an upper body including a plurality of longitudinal grooves formed around an outer circumferential surface, an inner cap having a wall with inner and outer surfaces and extending along an axis downward from all inside of the upper body, at least two protruding seals formed on the outer surface of the inner cap for fitting against an inside upper circumference of a bottle, a side reinforcement connected to the inner surface of the wall of the inner cap, wherein said side reinforcement extends longitudinally along the inner surface of the inner cap and is in axial alignment with said seals, and wherein said side reinforcement provides resistance against lateral movement of said inner cap, thereby maintaining a positive engagement between the seals of said inner cap and an inner surface of the bottle, and at least one stopper projection for catching on an upper portion of a bottle;
• a lower body connected to a lower end of the upper body and having a plurality of longitudinal grooves formed around an inner circumferential surface and at least one stopper projection;
• wherein an upper cutting line is formed between the upper body and the lower body except for a non-cutting portion;
• mid
• a vertical cutting line is formed such that the upper body and the inner cap of the upper body can be separated from remaining parts of the bottle cap, and a pull-tab is further provided to cut the vertical cutting line and to allow the upper body and inner cap to be removed from the bottle by a user.