ORIGINAL: Tired Old Man
A good gas carb can handle up to about an 8'' void of fuel in the line before the next influx of fuel is obtained, but rpm stability suffers badly. There is no reason for this when a felt filter only needs to make contact with the fuel to provide a constant fuel supply with virtually zero bubbles in the supply. There is also the fact that a felt filter making only that same basic contact with the fuel will sump nearly 100% of the fuel in the tank before the engine runs out of fuel. With most all other the pick up must be fully immersed in the fuel resevoir to function at all.
However, if some feel a pick up or filter needs to have a fancier appearance to suit their egos they always have the option of using the lower quality products. Eventually they will learn.
I started using these Walbro filters some 4 years ago (after reading one of Pat's suggestions for them) and since haven't looked back. I now have them in al my planes.
Since then, I have not once had to disassemble a carb to clean the screen from gunk and debris which used to be a common occurrence when I used the normal brass clunks
I have also noticed when I drain the tanks after a flying day, the felt pickup completely empties the tank.
They also have the added benefit that if the pickup momentarily comes out of the fuel in the tank (in high G manouvres etc), there is no noticeable stop to fuel supply to the engine
I buy mine from a local Stihl shop and normally keep a few handy on the bench