One of the reason pros like to slam their stem is the fact that the closer the stem is to the headset, the stiffer the stem, fork connection is. Deda designed the HSS (Headset Stack Spacers) to stiffen up the front end for those who cant slam their stem.

This spacer kit comes with three spacers, 3, 5, and 10mm. They’re made of unidirectional carbon fiber. So far, so normal.

Where they differ is these are designed to sit below the top cover of your headset, as in you pull the cover, install these spacers, reinstall the cover. They sit atop the headset and are wider than conventional stack spacers, both of which stiffen up the system.

These are designed to work with 1 1/8 steerers only.