The Flash Master works with most popular blade handles.  However, the blades are small and super-slim, so the important question is: Does your blade handle close completely?  If yes, you are all set.  We’ve tried it on a number of blade holders from many manufacturers.  If you’re in doubt, we know for certain that they will work with the X-Acto #1, the X-Acto #2, the Xacto Curve, and the X-Acto Griptster.  If your blade holder won’t tighten to a complete close, chances are that there is some oxidization on the threads.  (You may not have asked it to go that far in years.)  Usually backing it off completely and knocking some old gunk off the threads does the trick.  Reassemble and tighten without any blade in place to see if it closes until there is no gap in the blade slot.  Then, back off just a little and slide the Flash Master in place and re-tighten.