I have an FSA carbon crank on my bike and occasionally it makes a clicking noise once per revolution when I pedal. I have read quite a bit about this problem with this specific crank and so far have been able to retorque the allen bolt that holds the crank arm on. I know the bolt is aluminum and have read that some people have wrapped it with teflon tape and the problem went away. Where I need help is with the round "keeper" ring or spanner nut (not sure what it is called) that holds the allen bolt in. I can loosen the allen bolt but the nut on the outside of it needs to come out to let the allen bolt come out. This nut has a flat face and has holes evenly spaced for a special wrench to remove it. It has M27 #1 printed on it. My question is, what is the name of the tool I need to remove it and where can I get one?