Penn Plax Cartridges Fits Undertow and Perfect-a-Flow (2/Pkg.)</br></br><div style="text-align:left"><b>[Product Information]</b><br><ul><li>Ammonia Removing Undergravel Filter Cartridges are made with top quality zeolites which work to eliminate the top fish killer ammonia.</li><li>Undergravel Filter Cartridges solve the problem of overfeeding， over-crowding and foul water conditions.</li><li>This Filter Cartridges fit all Undertow and Perfect-a-Flow Filters.</li><li>Weight: 0.1500 lbs.</li><li>Cubes: 0.0004.</li></ul></div></br></br></br></br></br></br></br></br></br></br></br></br></br></br></br></br></br></br></br></br><img src='http://ecx.images-amazon.com/images/I/51FgEdIOo-L.jpg' noproxy></br>