A-UFO Bicycle Cycling Laser Tail Light Water Resistant 2 Laser 5 LED 7 Modes Adjustable Lock Ring Safety Back Rear LED Light Number of Modes: 7 flashing modes. Number of Emitters: 5 LED lights (Include 2 laser launchers). Easy to install: Buckle with adjustable lock ring (suitable for any size seat post diameter). The bicycle laser taillight can be used by 2*AAA batteries which may work 9 to 36 hours. The tail light used to improve the security of night riding and cycling entertainment.