Nylon and polyamide fibers have been a boon to knitting and crocheting since it was introduced in 1935. When nylon or polyamides are added to natural fibers it improves strength and durability of the yarn which is why so many sock yarns contain nylon or polyamide today. 

Twisted Ewe does not sell yarn with more than a 40% Nylon/Polyamide fiber content. Synthetic fiber is a great ingredient in many yarns where strength, elasticity and shimmer are wanted.