I can second that about those RJ-02 used as client headlamps for some time when caving(still do) all survived water mud etc… About 300lm brightness and with a good battery cell would run 12 hours plus at around the Mid brightness setting which is a round 120lm(uses ramping so is an approx) Best of all they cast less the £10(aliexpress) with battery and has USB charging (I sealed the charging port and use a nitecore charger for the batteries)

If you wnat cheap they are worth the money