Harri,
  My plans are to offer 21 watt to help dealers with inventory issues. The 24 watt will still be available as I will have 24 watt for
  video lighting. Why the change? It is mostly for inventory reasons and having too many choices. The 21 watt has 1500 lumens at 6500 kelvin
  and the 24 is 1800 lumens and 6000 kelvin. For a diving light the 24 watt provides no real advantages over the 21 watt and has a 20% less
  burn time., but for video the more light the better, so the 24's will still be available. We stock many different wattages of ballast and
  will continue to do so. I am trying to make it easier for dealers to stock lights. You can imagine how difficult it is for a dealer if
  they order all 24 watt and customers want to buy the 18 watt. I hope this helps, but always feel confident that all ballast and parts will
  always be available.