We added the ‘S’  for sonic to our SDM masts as on the top of the mast, there is a new construction which increases the reflex on the winglet area of the sail, giving more control and stability to the sail. 

K60 CARBON MAST: A very price-focused mast that can be used with all our sails.
The K60 offers good performance and enjoyment from any sail used with it. ‘S’ for sonic reflex. An incremented layer of carbon on the tip of the mast has been added. This will boost up the reflex on the top part of the sail. Save a bit of cash, and get the right bend-curve for the spine of your sail .2 layers of carbon and one layer of glass

WHY THIS MAST: A 60% carbon content sing the same high carbon quality as the more expensive masts and produced to the exact Point-7 standards for bend-curve and hardness as a K100. A better choice against an 80% or a 60% from a no name brand.