actually what I mean is that you have the standard foam inner filter and an outer foam sleeve that wraps around the filter... Mine wrap around the outer plastic housing that the foam goes in...... Like this.....
http://www2.towerhobbies.com/cgi-bin...&I=LXDNV5&P=ML
I think I use HPI brand but they fit my OS and other engines as well..... if I remember correctly... they are too big for the stock cen carb throat and thats why I used a motorsaver in that one.... As far as sand and water protection.. they work great..