Why this one
The maker's individual written reviews repeatedly describe audible output, compactness and durable construction.
Specifications and sources
What independent testers found
What owners report
Some are initial tests rather than emergency use. This meets the owner-pattern evidence route for a simple signal whistle, but does not verify a distance at which rescuers will hear it. The maker's 100 dB figure is not independently measured here.
Limits and cautions
- Keep it accessible and check that the intended user can blow it; an output rating does not guarantee a rescue response.
- Wet, muddy cave performance of the Mountain model was not independently tested in this pass.