How to measure
Palm: straight across the widest part of the palm, not including the thumb.
Length: from the base of the wrist to the tip of the longest finger.
Use the measurements rather than age alone. Hand shapes vary, so check both wherever possible. Once fitted, make sure the rider can comfortably use the throttle, brakes and every handlebar control.
Between sizes?
The larger size usually gives a more comfortable fit and a little growing room, but the glove must not get in the way of safe control of the bike.