Yeah 40 is small. It doesn't say on the package so I didn't know how tight they were until today. I guess I should notice any fuel starvation problems first on the Dura Force since it's the biggest fuel user. It's working fine for now.raying:75 micron is for use with fuel pump engines, 40 micron is pretty dang small. Might just have to change it more often.
I run the 125 micron red Briggs filters and the clear sintered brass filters. The red disk type fit better in tight spots.