USE SAFARI TO SEE THE FILE ONE END IS A LITTLE BIT WIDER/THINNER! MOUNT IT IN THE RIGHT WAY! JUST TRY BOTH SIDES - BEFORE - YOU SCREW IT ON. BE CAREFUL! - THE FEMALE/CORE THREAD OF THE NINEBOT ONE IS A BAD ONE (FOR EUROPE CONDITIONS/SCREWS) - SCREW IT SLOWLY ONTO. YOU`LL NEED SCREWS FROM YOUR LOCAL BIKE SHOP.