King Professional Muay Thai Shin Guards Size S - length of the shin: 14.17 inch , length of the instep 6.29 inch Size M - length of the shin: 14.96 inches, length of the instep 6.69 inches Size L - length of the shin: 16.14 inches, length of the instep 7.08 inches Size XL - length of the shin: 16.92 inches, length of the instep 7.48 inches