Smooth Silk 40 TightsSilky soft touch, flat seams and super resistant. The strength of a 40 denier with the looks of a 30. We use double covered yarn, where three threads are woven into one. A delicate, knitted waistline and a drop shaped gusset with flat seams gives the final touch to comfort, and also makes the tights invisible under clothing. Also, we added a sheer but strong reinforced invisible toe. All this together ensures strength and durability. They are designed