I originally ordered a hayward 800cx filter cartridge top,as mine was ancient and leaking,from amazon. The one sent to me had an air filter knob that did not go with the cap. I contacted inyopools and their chat person told me theirs came with the air filter knob attached. I returned the amazon one and ordered one from inyopools and it arrived within a few days and fit perfectly! All went smoothly and i am a satisfied customer.