I can get you any kind of bag you need. The 4 inch ring is called a p4 bag. I need to know the style of bag you want. PE,PP,nylon. 300 micron is the size of the particles the bag will filter out. E-mail me at
mdole@charter.net I work for a bag and media manufacturer and can supply any bag. The p4 will run about 3 or 4 dollars ea. depending on style and type of media.