Used this to replace an existing sensor (with identical part number). The old one would operate very quickly (you could block available light and the sensor would trigger within very few seconds) and with 100% reliability (on at dusk/off at dawn).
The new one is inconsistent, as it will sometimes remain on well after the sun is up or when the sky is overcast (reduced light), and I have blocked the light completely for over an hour without it triggering.
Would love to have a CP866 like the original one I had.