Sorry for what is maybe a stupid question,but if a truck is for sale specced with “wet kit” what does this mean 
Big Truck,
Wet Kit normally means Hydraulics, either to power a tipper or more often as a tanker unit with a hydrapac.
Some road barrels have a compressor and cargo pump mounted on the trailer chassis, so all you need is a hydraulic tank, and pto driven pump on the unit.
Cheers Wheel Nut 
I learn something new evry day… today I learnt from you … thanks 