The Echomax have come out well in various reports over the years - British design and manufacturer. The alternatives are the Tri-Lens or the much more expensive Sea-Me active reflector. Don't bother looking at the basic tube types though.
We have the Echomax and Tri-Lens available, with more info on the website.
I use the em230 with the all-round white light. Looks a bit chunky sat on the A frame (rudely described as a dustbin on one occasion), but when we've run joint exercises with radar equipped boats they've told us they get a pretty good return from us.
