Old dirty diagram,but it does show all the principal measurements for the boats and the sails. And for those who are still wandering about a 150% or 130 or 110, etc, it is simply the LP/J ratio. Of course the greater the ratio, the greater the surface area of the sail. The J measure goes from the base of the mast to a point in line with the stay attachment point. It is calculated at a precisely 90 degrees angle from the mast. SPL stands for Spinnaker Pole Length and G stands for the Girth of the spinnaker. LLJ = Luff length Jib. LLS = Luff length Spinnaker