The Personnel Marker Light (PML) is a safe chemical light approved by the USCG and the FAA for use on life preservers.  Squeeze handle to activate.  When activated, the PML emits a yellow-green glow which lasts for a minimum 8 hours & is visible up to 1 mile on clear, dark nights.  A superb emergency light source for life preservers as it is waterproof, windproof, nonflammable, easy to activate, and requires no batteries.  Four year shelf life.