The Flex back strap wraps around the back of the hoof, over the heel bulbs, and attaches securely to both sides of the boot, using ball rivets connected to the boot shell. Back strap is included as part of every complete Flex Boot. If you need a replacement or would like to customize your boots, you can also purchase back straps separately in a variety of colors. Flex back straps are available in multiple color options, giving you the freedom to personalize your boots, and five sizes to suit different boot sizes. The same back straps are compatible with both Classic and wide Flex Boot styles.