SOLO™ FEATURES: » Completely re-designed. » Super-thin, ergonomic, comfortable curved design. » 3 selectable warning altitudes » 1st and 2nd warnings: Different pulsating tones » 3rd warning: High pitched siren » Choice of 1, 2 or 3 warnings » Easy and quick to set on the ground or in the aircraft » Altitude selection interval: 500 Ft. » On/off mode » Built-in mounting holes; fits any helmet, inside or outside » Long lasting, easy to find batteries