Short video.
Concrete Work
The more air bubbles you have in your concrete, the weaker its structural integrity when it hardens. A concrete vibrator is a concrete tool that produces stronger concrete by vigorously shaking the concrete right after you pour it to eliminate the air bubbles or air pockets.
Needle vibrator: These are also known as immersion, internal, or poker vibrators. A needle vibrator can be used for any type of concrete work. This consists of a steel tube, called poker, having an eccentric vibrating element inside it, a flexible shaft, and a power unit.