Useful timing advance ring for when you are using a boost pin or playing with fueling as this enables greater range of dynamic timing. Less smoke/cleaner burners means more power and happy MOT man. Won't do anything for power on its own.
Ring is well machined and comes with two genuine seals (some kits provide one and make you reuse your old one) also surprisingly they included a torx bit.
Easy job to fit with instructions. The only caveat to "easy" is on a Land Rover Discovery there is very little space with the pump on the engin so you can't get a socket wrench in there. I used a torx "Allen" style key and even then needed to do tiny turns and reposition the tool. Bit of patience and they come out.