Thomson’s X2 is machined from a billet of 7000 series aluminium, and features two bolts on the front cap and two on the steerer tube clamp. It is essential that you use a torque wrench on two-bar clamp bolts.
To keep the same level of stiffness as a four-bolt setup, the X2’s front cap is shaped so that two cutouts on the stem mate with corresponding sections on the cap. This reduces the chance of the cap rotating.
The X2’s stack height – the total height of the steerer tube clamp – is just 36mm. This means that you can get your handlebar super-low if you want, but does also mean you will need an additional spacer if you’re switching from a stem with a taller stack, so check when buying.
The X2 can be flipped for positive or negative rise. The +/- 10-degree model comes in 70, 90, 100, 110, 120 and 130mm lengths; the +/- 17-degree stem is available in 100, 110, 120 and 130mm versions. It has a 1 1/8in steerer tube clamp and is available for 31.8mm bar clamps.
The 110mm/10-degree X2 is light for an aluminium stem, especially one as rigid as this, but you will need to factor in the weight of aluminium spacers if you want to increase the height.