Ours is a 36C and we use a Forespar ( I was going to buy a Seldon, but this one popped up new shop soiled with a scratch on it at half the cost!) whisker pole - telescopic 2 pc. About 55mm dia OD I think from memory. It extends to about 3.5m but I don't use it at that length, or haven't yet. We wanted a light pole because we only have a for hoop on the mast and not the full track mast mounted system, which would have multiplied the overall cost by about five.