【Perfect Replacement】Works for these spa filters models: Unicel C-6430, C-6330, C-6430RA; Pleatco PWK30, PWK30-M, PWK30-3, PDC510-AFS; Filbur FC-3915, FC-3915M; Watkins 30/Hot Springs, 31489, 71825, 71826, and more hot tub filters. 【Dimension】Outside Ring Dia: 5-7/8'', Inside Ring Dia: 1-15/16'', Height: 10-1/2''. Exact the same size as your old one. (no built-in chlorinator) 【Solid Structure】Enclosed thick pleated fabric combined with a strong plastic internal support frame holds shape and is not easily deformed when pool water flows through. 【Efficient Filtration】 The ultra-fine sturdy trilobal filter paper grabs sand, sediment, hair and leaves more than regular fabric. Allowing for greater capacity and debris reduction. 【Last Long】They are durable, easy to clean with a garden hose and reused several times, greatly extending the life of the filter. Save your budget.