Made for those of us who like to get rowdy the Chromag Director Stem is a stylishly crafted piece of kit for downhill bikes with 31. 8mm handlebars. This piece of kit might seem a little dated, but when we're running downhill runs with our 31. 8mm bars we're all but guaranteed to have less hand fatigue over a long day. 31. 8mm bars flex a bit more than 35mm bars, so they're soaking up harsh vibration and chunder all day long.