The Box Two Hollow Center Clamp stem is cold forged from the highest quality 6061-T6 aluminum available. Featuring an open skeletal design and a dual mid-bolt wedge mounting system, they are lightweight yet maintain a very high level of strength. A 53mm extension stem weighs just 218g (7.7oz). By removing the rear pinch bolts and moving the mounting bolts to the middle of the stem, Box reduced the weight, size and eliminated a serious hazard to the rider's knees. These stems come with either a 48mm or 53mm extension and have a 22.2mm clamping diameter. To ensure proper clamping force, the stem must be mounted on a fork with at least 45mm of exposed steerer tube. Not compatible with forks that have carbon fiber steerer tubes. ###section### Product Specs TYPE: Front Load REACH: 40 - 53mm RISE: 5mm CLAMPING DIAMETER: 22.2mm WEIGHT: 213g (7.52oz) Colour: Black, Blue, Red; Size: 48mm, 45mm, 53mm, 40mm