Four MaxFlow Mesh Media Filter Bags with Zipper - 3 Inch by 8 inch  UNIVERSAL BIO MEDIA BAG – Aquarium mesh bags fit any large filter media, especially biomedia like bio balls, zeolite, ceramic media, rock, and crushed coral. Pick the right size bag to fit your fish tank filter: sumps, canister filters, and power filters. Perfect for your freshwater, saltwater, or reef tank, small or large. For charcoal, carbon, and other small media see our other media bags. CUSTOMIZE YOUR AQUARIUM - Choose the filter media best for your fish tank, in the amount you need it. Our mesh bags let you optimize your filter to meet the needs of your aquarium or pond and the fish and livestock you have. We have the right size bag for your filter, large or small. Get the water quality you want! SAVE MONEY – Media mesh bags are durable and reusable. Buy filter media for your fish tank or pond in bulk and reuse the bags. When the media needs to be changed, empty the bag and refill it with fresh filter media. This pack comes with FOUR BAGS. AVOID THE MESS - The secure bag zipper means you don't have to worry about media spilling out into your filter and into your aquarium or pond. The durable mesh bags won't tear open, keeping the filter media locked up tight. MAXFLOW bags have 2 mm holes for optimal flow for bio media, but WILL NOT hold small media like carbon pellets. PROTECT YOUR PETS - The mesh is completely nontoxic and safe for freshwater, saltwater, reef tank, and pond use. The plastic zipper has no metal parts and will not rust or degrade. You can click the yellow “Add to Cart” button today with confidence— knowing that you are getting the best media bags!