I use these. These are meant for the 5.5mm carb cars. Aka their .21 sized or large .12 carb size.
http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MESE:IT
There exactly like the RB filter and you get 2 for the price of one.
If you race , this is what everyone uses. You get tons of surface area and its one-piece so sand cant sneak through the sides.