Ballpoint pen. Shaft: Made entirely of stainless steel with scratch resistant PVD-coating. Materials: Large black ink cartridge. If you push the mechanism of the Porsche Design Tec Flex Black the stainless steel weave responds to the pressure of the hand and pull together. After you release the weave goes back to its original position.The TecFlex line from Porsche Design employs a stainless steel mesh borrowed from the racing world. The extraordinary flexibility of this material perfectly suits the nature of the products.