Just as a caution and reminder to others, these lights aren't supposed to use 10440 and can easily fail from doing so.
been using mine for over a year now. no problems whatsoever. just have to be cautious if it gets too hot, turn it off and let it cool, also, for longer usage, leave it on low or medium. and medium on a 10440 cell is brighter than a max on a AAA battery.
using the 10440 on the iTP A3 greatly increases its runtime and extremely big boost in lumens. mine puts out easily over 200+ lumens.
lastly, if you check the specs of the iTP A3, it's rated up to 4.2volts, so i'm just maximizing it's capacity.