Mini Electronic Pulse Stimulator (TENS/ES Unit). For muscular pain management and muscular stimulation, hence called TENS, which stands for Trans Electrical Nerve Stimulation, and ES means Electrical Stimulation. Brand new and sealed. My old profession as a Physical Therapist, this modality used to be expensive. With today's new technology made it affordable to keep you from constantly seeing your physical therapist, paying co-pays from $50 to $90 per session or more depending on your medical insurance and state you reside. The TENS function is for muscular pain management, whereas the ES function is for muscular stimulation to help muscle fiber twitching for muscle weakness. This is one modality a Physical Therapist carries for home care and for his or her clinical private practice.