The origional "Baja filter" was a 8" deep, x 8" wide x 24" long SS box. There were 3 dividers, each of which had five 2" holes in them covered with fine bronze screens, in decreasing size in each hole in the box. The last section had a 1 1/2" pipe which fit into the fuel tank fill--with the box sitting on the deck. This filtered the fuel quite well, and trapped any water which may have been in the fuel. We used this type of filter for many years in Mexico--but more recently the fuel supplies in Mexico have become more reliable (not as much out of old 50 gallon drums).
This is a bit large to use on a C Dory or Ranger. I have used the plastic filters/funnel as described in the Practical sailor article more recently. This also is faily effective at trapping water. We tried the more modern, round Baja filter and found it was more awkward, and did not work as well as the older box filters. When the upper part was full of fuel, the filter was a bit unstable. The problem with any of these filters, is that they slow the intake of fuel, but this may be a necessity with small fill ports.