This filter cartridge is a replacement part for the BKP portable filter. The BKP Single-Cartridge Portable Filter is now complete! This is the most handy, heavy-duty pool service device available. This unit combines the strongest workhorses of the industry to provide years of dependable service under the most extreme conditions. Imagine being able to say to a customer “No Problem!” on a daily basis! Every pool service company, pool builder, or aquatic facility should have a BKP Portable.