Concentric needles are used during Electromyographic (EMG) examinations. The EMG measurement is performed by inserting the needle, which contains both the active (core) and the reference (cannula) electrodes as close as possible to the potential of interest. Finally, a ground electrode is placed relatively away from the needle.
Sold in packs of 25 pre-steralized single user needles
Concentric EMG Needles
Hypodermic EMG Needles