Another popular knitting machine is Shoes Upper Knitting Machine, which is mainly circular knitting machine. Compared to warp knitting machines, circular knitting machines create shoe upper material that offers better breathability, more design possibilities and less waste. Even when used for more casual physical activity, athletic shoes must be designed in a way that keeps feet cool and dry. Because of this, the vast majority of shoe upper material is made using spacer fabric. http://www.tckjknittingmachine.com/shoes-upper-knitting-machine/