Poolmaster 13040 Replacement Filter Cartridge for Star Clear II C1100 CX1100RE Filter Equivalent to the following replacement filter cartridges; Pleatco PA100-4 and Unicel C-8610 The top of the replacement filter cartridge is open 4-1/16 molded gasket and the bottom is open 4-1/16 molded gasket Break-resistant bands keep pleats separated for greater flow, filtration and add longer life to cartridge High quality spun bonded polyester material for exceptional water filtration Premium grade polyurethane and plastisol end caps