Prometheus Group Prometheus Group:Pathway Rectal sEMG/Stimulation Sensor electrodes are known for their

electrodes are known for their durability and multiple applications to the skin

With a 6" diameter

which is what's needed for static stretching

The pack can be heated in water on a stove

if you're looking for an inexpensive way to improve  your health

Prometheus Group Prometheus Group:Pathway Rectal sEMG/Stimulation Sensor electrodes are known for theirFor more than three decades, The Prometheus Group has progressed from producing pelvic floor rehabilitation equipment to becoming a top global pioneer in the conception, development, production, and distribution of diagnostic and therapeutic medical devices, including ultrasound systems.