I am sory if this is an off topic but I was wondering what kind of tow rope is best for a ski lengthwise and width of the rope ,I see that they are using yellow nylon stern line ropes any info will be welcome !!!

The Armstrong ropes are good mate. They are the thick yellow ones you have seen. You can order online directly from Armstrong.I use a relatively short rope approx 2/3 of std length but it is a personal thing I think. Too short puts you in the jet wash on takeoff too long and it's harder to time waves.

hope this helps.

Here's a good but expensive option. The rope floats (easy to spot) and because of the thickness, it's much less less likely to get sucked into the intake. Because of the thickness, you could also grab the rope anywhere, not just the handle.

highsurfrescue.com/product/the-hybrid/

The hardest towing is DW prone as the sea is rough as guts......rope too long and you get pulled through the waves as the boat goes over the one in front and whips are harder to co ordinate ...rope too short and doesn't work either. About 7m seems to be the best, and nylon ski rope with 10mm foam noodles fed inside it to make the rope float on the surface.Some kind of quick release at the boat end is handy if towing in the surf break as you can dump the rope if a set comes and the rope/ handle is accidentally caught in the foil or leg rope.