BOX ONE TOP LOAD STEM 31.8mm 1-1/8"

Product Overview

The Box One Top Load Stem is a cold-forged and CNC-machined aluminum stem designed for 1-1/8" steerer tubes and 31.8mm handlebars. Available in 48mm, 53mm, and 60mm reach options with a 0-degree rise, it uses a top-load clamping design for handlebar installation. Built from 6061-T6 aluminum, it provides a durable, precise connection between fork and handlebars.

Key Features

• Cold-forged and CNC-machined 6061-T6 aluminum – Cold forging increases material density and strength before machining, resulting in a stronger stem at the same weight compared to standard machined stems
• Top-load clamp design – Handlebar clamps from the top with front-facing bolts, making bar installation and removal easier than side-load or front-load designs
• 31.8mm handlebar clamp – Standard oversized clamp diameter provides better clamping force and reduces handlebar flex compared to 25.4mm stems
• Multiple reach options – Available in 48mm, 53mm, and 60mm extensions to accommodate different rider sizes and handlebar positioning preferences
• 0-degree rise – Flat profile maintains consistent handlebar height relative to the steerer tube

Technical Specifications

• Material: 6061-T6 aluminum alloy
• Clamping Type: Top load
• Steerer Tube Diameter: 1-1/8"
• Handlebar Clamp Diameter: 31.8mm
• Rise: 0°
• Reach Options: 48mm, 53mm, 60mm
• Weight: 287g (53mm; other sizes TBD)
• Steerer Clamp Bolts: M7 x 22mm (P1.0 thread pitch)
• Handlebar Clamp Bolts: M7 x 22mm (P1.0 thread pitch)
• Color Availability: 60mm available in black only; other sizes may have additional color options

Compatibility and Ideal Use Cases

This stem is compatible with any 1-1/8" steerer tube (threadless) and 31.8mm handlebars. Not compatible with 1.5" or tapered steerer tubes, or 25.4mm (standard) handlebars. Works with integrated, semi-integrated, and external cup headsets that accept 1-1/8" steerer tubes. Ideal for riders using modern oversized handlebars who want a strong, reliable stem with easy bar installation. Choose reach based on rider size and preferred handlebar position—shorter reaches position bars closer to the rider for quicker handling, while longer reaches provide more reach and stability. Note: Ships direct from manufacturer if located in the USA, which may result in separate delivery from other items.