A word of warning about pole lengts.
I recently bought 2 supposed 18ft lightweight poles from a well known supplier.
My lads had been using universal 18ft ones on domestics and had no problems really but in a rare fit of generosity I thought I would be making life a bit easier for them with lightweight poles. They complained to me that the new ones were harder to use because they didnt reach as high as the new ones. I thought they were being nit-picky but I fully extended the new ones, laid them on the ground and measured them. My nice shiny new 18ft ones are a tad under 17ft long!
I contacted the suppler to be told the 18ft is "reach from hip height" So I suppose they must measure the height from the ground of every customers hips.

I will be taking it up with the supplier but in the meantime I will always now ask the actual length of a pole. Maybe it's worth posting this for others who are under the impression that 18ft means 18ft. Or any other length for that.