the peguin filter has the larger slot because the ysell a media container for them i bought 2 for my peg,350, they hold carbon or any thing smaller.. i also use the fosters and smith clam shells, and put filter batting in them with or without carbon.. i don't like the peguin filters lets too much stuff thru..
http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=13370&N=2004+114140
just use the plastic and add the filtering media of your choice..
http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=13370&N=2004+114140
just use the plastic and add the filtering media of your choice..