Big Brand Water Filter Industrial bag filters come in #1 and #2 sizes. #1 bags are 7" by 16" and #2 bags are 7" by 32". Bags are avaialable in polypropylene and polyester materials. Welded bags give better particle reduction than sewn bags. Monofilament bags are available in polyproylene and nylon. We also make bags for #3, #4 and #5 size housings.