The 1-1/8in ShockStop stem fits standard 1-1/8in (28.6mm) steerer tubes which is the size used by most modern bikes. With the introduction of our new 1-1/4” version, the Shockstop can now be used on popular brands such was Giant and Canyon bikes.
The easiest way to determine your steerer tube size is to use a pair of calipers to directly measure the diameter or take your bike to the local bike shop and they will be able to measure it for you.
If you don’t have easy access to either a shop or a set of calipers you can check your manufacturers website. Most of the time a manufacturer will list this under their specifications in the Frame/Fork section. Make sure you are looking at the correct model year as these sizes can change year to year.
Alternate method: Use a fabric or paper measuring tape (or print one at https://printable-ruler.net/ ) and measure the circumference of the handlebar right next to your existing stem.
A 1 1/4”(31.8 mm) steerer clamp will be 99.9 mm in circumference at the center.
A 1 1/8” (28.6mm) steerer clamp will be 89.9 mm in circumference at the center.
A 1” (25.4 mm) steerer clamp will be 79.8 mm in circumference at the center.