The CMP 378900 R is a compatible replacement for the following spa filters:
The Custom Molded 378900 Comp. Pool Filter Cartridge is a spa filter replacement measuring 4 1/4" x 4" with 10 sq. ft. of media area. This compatible Custom Molded Products filter features a 1 15/16" Open top style and 1 9/10" Open bottom style with Slots. This spa filter cartridge ensures premium purification of your pool/spa.