Corekits and Materials Core material kits consist of up to 1600 unique items used to increase the durability and performance of wind blades. By combining the right thickness and sizes and cutting them into the right shapes, a kit becomes a lightweight yet sturdy component to support the wind turbine blade. A kit usually consists of shells for the lower and upper part of the blade and a vertical web in the middle for extra support. Our kits are made from your choice of PET foam or balsa wood. Both are materials with a high stiffness-to-weight ratio, but while balsa is a natural wood grown in Ecuador, PET is a foam made of recycled plastic all around the world.