Originally Posted by discomick
Do I need one if I have AIS fitted.
SOLAS requires all vessels to carry a radar reflector wherever practical, it makes no "exemption" for vessels fitted with AIS transponders.
Only vessels with AIS receivers fitted will see you. Small craft (including fishing vessels, yachts, other, ribs etc) may not have a receiver fitted (or being properly used) but MAY have a radar fitted - they will expect you to have a radar reflector fitted.
There is at least a theoretical risk in busy waters that you don't show up on AIS due to the "clutter" from other users hogging the spectrum.
If you have an electrical failure AIS will not transmit. A passive radar reflector will.