The Locking Knob for Pool Filter CX900G is a vital replacement part compatible with Star-ClearPlus filter cartridges. It ensures secure and efficient operation of the pool filtration system. Made with high-quality materials, this knob provides reliable locking and adjustment for proper maintenance of the pool filter. CX900DA Knob Replacement Kit. The installation is fast and simple, Only delay was e ring on due to some corrosion in the groove. It helped to assemble the e ring on knob first and rotate it until free-er to move, then remove, and assemble once the knob was back on the filter head. Type: Pool & Accessories Feature: , Easy to Install Colour:White Material:Plastic Package Contents: 1x Element Guide Cone 1x E-Ring 2x Spacer 1x Sealing Washer Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.