Hayward Locking Knob (C751, C900, C1200 series)

The Hayward CX900G is the locking knob for Star Clear Plus cartridge filters, models C751, C900 and C1200. It is also the knob on the Pro-Grid DE separation tank DE-900 and DE-1100. Genuine Hayward.

What it looks like

A black plastic four point star top with a brass stem molded into the bottom. The stem is 1-1/2 in. long and carries two grooves, a small one at the bottom and a larger one toward the top. If your old knob matches that description, this is the part.

Order the seals with it

The knob o-ring, the washer and the E-ring are separate parts. A knob that has been leaking or spinning without locking usually needs its o-ring replaced at the same time.