Vibrators needles are the most commonly used concrete vibrators. It consists of a steel tube (with one end closed and rounded) having an eccentric vibrating element inside it. This steel tube called poker is connected to an electric motor or a diesel engine through a flexible tube. They are available in size varying from 25 to 75 mm diameter. The diameter of poker is decided from the consideration of the spacing between the reinforcing bars in the form work. The frequency of vibration varies up to 3000 RPM. However, range between 3000 to 6000 RPM is suggested as a desirable minimum with an acceleration.