Review on 🐠 Aquarium Bio Ceramic Rings for Canister Filter - Efficient Water Changers for Fish Tank by Sonya Oberembt

Good one Priced at $12 for 4. Very porous and will absorb water all the way to the top if only the bottom of the cylinder is wet. Did a fishless tank cycle with them and got a nice quick cycle. They have imperfections such as chipped corners, paint stains, 2 cylinders melted together, etc. The zippers are light, the prongs are plastic with fabric strips (good). I can't tell what the train is made of, but it's NOT magnetic so either plastic/aluminum/or stainless steel.