"Dear Sir, I need your help please. I have just bought a spider putter. Can you tell me the feet ratio's to 25/50/100/150 and 300 ft please. What length is each movement of the putter. I await your reply in anticipation. Molineux"
It's easy enough to work out for yourself - as you take the putter back, every now and again it moves. Take it back fully and count the number of moves it takes to get to the max, then divide the max footage by the number of moves to get there. You have to watch Green Speed though, as on faster greens the ball obviously rolls further. On my putter, from fast to very fast greens it goes one half further.