Someone mentioned Zebralight has dropped the release date on their spreadsheet for the Q50 but have a 2012 release date for the S5310. 3AA, 0.1-750 lumens, 1.47"Ø 3.5" long.
Just remember the Q50 is 1.3" across the flats, diagonally it is more than the 1.47" of the S5310.