# K251856: Li-Battery Powered OTC TENS/EMS Combination Stimulator, Model Z4

- Pathway: 510(k) (Special)
- Applicant: Everyway Medical Instruments Co.,Ltd
- Decided: Nov 21, 2025 after 157 days
- Product code: NUH (Stimulator, Nerve, Transcutaneous, Over-The-Counter)
- Device class: 2
- Regulation: 21 CFR 882.5890
- Recalls of this device: none
- Data: FDA decisions to Oct 25, 2026; recalls to Oct 12, 2026

## Lineage
Longest line of descent: 1 generation back to K201335 (2020). 1 ancestor in all.
No later device cites it as a predicate yet.
0 of 2 devices in its family (counting itself) have a Class I recall.

## Predicates on the family tree (from the FDA summary)
- K201335: Li-Battery powered OTC TENS/EMS Combination Stimulator, Everyway Medical Instruments Co.,Ltd (2020) Summary page 5.

## Indications for use
1. The Z4 Li-Battery Powered OTC TENS/EMS Combination Stimulator is intended for over-the- counter (OTC) use. It integrates both TENS and EMS functions in a single unit. However, the device can only operate in one mode (either TENS or EMS) at a time; simultaneous operation of both modes is not possible. 2. TENS is intended for temporary relief of pain associated with sore and aching muscles in the low back as well as upper and lower extremities (arm and/or leg) due to strain from exercise or normal household and work activities. (Choose TENS Modes P1 to P19 programs) 3. EMS is intended to stimulate healthy muscles in order to improve or facilitate muscle performance. (Choose EMS Modes P20 to P30 programs)

Source page: https://510kreport.com/device/K251856
Methodology: https://510kreport.com/methodology