These Filter Media Bags come in a choice of grades, so you can use a selection of media within them. The black, coarse grade bag, is ideal for use with biological filtration, such as bioballs, either plastic or ceramic, and other larger items, like charcoal, or alfagrog.
The finer grade white bag is better suited to smaller media, such as carbon or zeolite.
These bags measure 10" x 12", and both come with a zip opening, so they are more secure than standard drawstring bags. They can be partly filled and used in smaller spaces, like filter compartments, or filled right up for sump use.