50 SQ FT Open Filter (Slip)This spa filter offers 50 sq ft of genuine Reemay material, helping to keep your spas and hot tubs cleaner for longer. This filter can be used in place of the following models: Unicel C 4950, Filbur FC 2390, Pleatco PRB50 MIN, Aladdin 15002. NOTE: Filters should be changed every 4 6 months (depending on usage). For best results, clean your filters regularly using Canadian Spa Company's filter free cleaner solution. 50 sq ft filtration surface area