My son is 6'4" and the (fully extended) upper strap could not make it around his lower thigh (above the knee) without being too tight.
Careful how you measure the leg - seems to run small. We were looking for a replacement for broken 17" All-Star shinguards, and the 17" Nike was shorter. The Nike has a full length knee-shin pad, which is nice, but the knee pad is not as thick/cushioned as the All-Star (which does not extend the pad down the shin). The guards seem lighter weight compared to the All-Stars, which may be a plus.