KIDS BIKE SEATS WITH FIXED STEM THE STEM SIZE IS 22mm IT SAYS 22.5 ON THE STEM BUT I MADE IT 22mm PLEASE MAKE SURE THE STEM SIZE IS THE SIZE YOU NEED AS THEY DO VARY IN SIZE,THEY ARE STARS DESIGN I AM JUST CLEARING THEM THEY ARE NEW BUT MAY HAVE A ODD STORAGE MARK BUT NOTHING,WILL POST.