Our Technora Toughlaces are the strongest, most burly boot/shoe lace ever created. They are 8 times stronger than steel, fire resistant up to 932 degree F, highly abrasion resistant, and hard as hell to cut. The Toughlaces are made from Technora fiber which is a high tech aramid like Kevlar, but better as it excels in flex fatigue which means it is commonly used in fire rescue ropes to save lives, body armor to stop bullets, and high performance sails to win world cup races. To make sure our laces are the toughest ones on the planet we braid them as dense and tight as possible. But we don't stop there, because a lace is only as good as its tip. So we fit the ends with a crimped on metal tip. No plastic to split and fall off. The results are bootlace that will outlast your boots. And if they don't, send them back for a free replacement. Like all of our products, these are designed, tested and made by us, on our braiding machines and finished in house by hand, right here in the USA. They are sold as a pair. Diameter: 9/64"(3.5mm). Break Strength: Not rated but exceed 1,000lbs. For exact sizing, its best to take the old laces out of your shoes or boots and measure them with stretch, as our laces do not stretch. If you need a custom size, buy the next largest size and write a note in the order sections of the size you need.