Standard Flat Lace come in 35 colors and 5 different lengths and a plastic tip. Found on most sneakers and shoes.   Generally, a flat  lace will stay tied more easily than a round lace with a core because the flat  lace can be more crimped within the knot. Shoe Laces offer the best way to fit a shoe ... dress, running or otherwise ...to the human foot. Laced footwear is more secure on the foot than slip-on styles and, depending on the structure of your foot (like high arches), provides a more comfortable fit.