Ritchey 31.8- mm 28.6 Bicycle Stems
About Ritchey - "Ritchey bicycle components have been raced to victory in some of the biggest cycling competitions in the world including the UCI World Championships, the Tour de France and the Olympics and it all began in a simple garage in Menlo Park, California with Tom Ritchey.'
Bar clamp diameter is the diamater of the handlebar.
S.H.I.S clamp diameter is the steerer tube diameter.